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IPTC 2013: International Petroleum Technology Conference
- Conference date: 26 Mar 2013 - 28 Mar 2013
- Location: Beijing, China
- Published: 26 March 2013
41 - 60 of 581 results
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Optimization Study of Production‑ Injection Ratio for Steam Flooding
More LessProduction-injection ratio (PIR) is one of the most important factors to affect steam flooding performance. Previous research and field applications of steam flooding have confirmed a common conclusion that the production- injection ratio should not be less 1.2 to achieve higher oil recovery for a conventional heavy oil reservoir. This paper presents the optimization study of production-injection ratio for an unconventional heavy oil reservoir with edge/bottom water. Aimed to Jin 45 Block of Liaohe Oilfield, experimental and numerical simulations are carried out and sensibility analyses are focused on the effect of aquifer size. Compared to the conventional heavy oil reservoir, the results of this study have validated as follows: (1) The optimum production-injection ratio (OPIR) of Jin 45 block steam flooding is significantly dependent on the size of its aquifer. Actually, if only the reservoir pressure is available to steam flooding, the OPIR will reduce with aquifer increasing. (2) With the aquifer increasing, the reservoir pressure before steam flooding will relatively increases, thus steam specific volume decreasing and production-injection balance point removing. (3) The difference of production-injection ratio reflects a balance relationship between production and injection underground. For a heavy oil reservoir with edge water, production-injection balance should be completely maintained to prevent water invading which will seriously lead to bad thermal efficiency of steam flooding. (4) Note that the OPIR should be understood as an average concept. Essentially, the production-injection ratio is differently implemented at different stages of steam flooding. Hence, the interval ratio will be corresponding different. This paper suggests that actual reservoir condition and production performance should be globally taken into account to optimize the production-injection ratio at every stage of steam flooding. It is a considerable strategy to satisfy the management requirement of steam flooding program.
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New Offshore Sidetrack Practices Reduced Significantly Stuck Pipes in KSA
More LessThis paper demonstrates the causes of the major issue of stuck pipes in offshore sidetracks in Saudi Aramco & also explains the new drilling practices implemented to reduce the number of stuck pipes while drilling or running completion systems. Out of three wells sidetracked, two stuck pipes occurred. Year after, this number of stuck pipe has declined significantly after revised and corrected drilling practices. In year 2005, oil demands went up and therefore, Saudi Aramco converted vertical and deviated wells to horizontal in order deliver more oil to the oil market. Sensitive shale instability problem was present almost in every well where drill pipe got stuck. Also, it is worth mentioning that development of humps while drilling contributed to inability of cleaning the hole very efficiently. Typically, every single well is sidetracked and drilled across shale formations of different pressures up to the productive zone. After drilling the horizontal section, the whole well is reamed with stiff assembly during which obstructions and tight spots are cleared. Then, ICD system is deployed to TD. This paper will highlight the main causes of stuck pipe and following that, successful solutions will be presented and explained in detail.
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Well Integrity During Operating the First Offshore Gas Wells in Saudi Arabia; Experiences and Lessons Learned
Authors S.M. Alsyed, E.A. Uzcategui, R. Adesegha and A.S. Al-AhmariAnnulus pressure is an important key to maintaining Well Integrity. During the start-up of Saudi Arabia’s first offshore nonassociated gas field containing high pressure high rate sour gas wells, a continuous increase of some annuli pressures was experienced despite the fact that these annuli were cemented to surface. During any well production, the heat transfer from the produced fluid to the trapped annuli fluids causes annuli pressures to increase to levels that could exceed collapse and/or burst pressure limits of the casings. This is especially true during early startup of the well when all annuli fluids are cold (offshore wells) or at ambient temperature (Onshore wells). To ensure that the pressures does not exceed the maximum allowable limit of well tubular various calculations were performed, taking into account not only the tubular limitations but also the formation pressures these casings encountered, to set the maximum limit. Periodic bleeding of pressures and continuous monitoring was necessary to avoid reaching this maximum set limit for the first four months of production. In this paper performance of the different annuli is analyzed and discussed. Calculation methods are also discussed in details which were employed to determine the maximum allowable pressure limit for each annulus. Elimination of frequent bleeding of 1st casing-casing annulus in one of the wells by revisiting the maximum limit, taking into consideration the formation pressure the casing was set in are some of the lessons learned documented during this first offshore gas field startup and will be put forth in the paper.
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Casing While Drilling (CwD): Surface Hole Optimization in Mature Field of Offshore North West Java
Authors H. Taufiqurrachman and E. TanjungOffshore North West Java (ONWJ) is one of Indonesia's mature fields. Mature field developments in this level require a simple, fast and cheap well design to be economically interesting. The highlight in this paper is drilling top-hole section optimization by applying Casing while Drilling (CwD). The main 2 challenges in drilling top-hole section in ONWJ are gumbo attack and loss circulation. Past mitigation was drilled a small pilot hole to reduce cutting amounts then enlarge the open-hole by hole opener. However it did not solve the problem completely. The gumbo attack still occurred, some associated non-productive rig times still happened and safety concern to clean the plugged flowline still existed. KCl Polymer mud system was not an option due to loss circulation existence, where hole will collapse when seawater is displaced to keep hydrostatic. CwD were executed successfully at 2 exploration wells in Q3 2011 by implementing Vertical-CwD (VCwD). First trial of VCwD was run only in surface section with a simple cutters casing shoe mounted on the end of a casing string. Further improvement in drillshoe, BHA and mud design was made on the second trial to extend the interval and improve overall ROP. The second trial of VCwD managed to safely drilled almost 3000ft of combine surface and intermediate vertical section with overall ROP of 60fph, where at surface section CwD was performed blindly due to total loss circulation and it was successfully cemented (no annulus pressure trap so far). The second trial has saved the company over 1MMUSD compared to conventional drilling. In 2012, numerous trials of Vertical Casing while Drilling (VCwD) have been performed for exploration and development wells in offshore North West Java. CwD is heralding the way to the future of drilling in mature fields of Offshore North West Java.
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Integrating Pressure Transient Analysis and Production Analysis for Dynamic Reserve Evaluation in Tazhong 1 Ordovician Carbonate Gas Field, Tarim basin
Authors S. Hedong, S. Ying, L. Shiyin, K. Bo, L.U. Linlin, S. Zhicheng and L. YanchunTazhong Ⅰgas field is a typical vug-fractured marine carbonate gas condensate reservoir with characteristics of high heterogeneity and complex geological & dynamics, of which grand challenges face the development by using the classic evaluation method of dynamic reserves. On the basis of literature research, a formal definition about dynamic reserves is given. Besides, a workflow of dynamic reserve for carbonate gas condensate reservoirs is built relying on the long-term lowaccuracy data of daily production and short-term high-accuracy data of pressure build-up testing, which integrates full life cycle short-term pressure transient analysis and long-term production analysis combined with the geological understanding. The factors affecting reserve estimate are analyzed based on a field application on TazhongⅠgas field, including initial formation pressure, PVT, the error of pt~pwf conversion, production time, producing water and routine of work. The simulation results show that the gas-liquid two-phase pseudo-pressure method is more appropriate than the pseudo-ingle phase method for calculating dynamic reserves for low gas-oil ratio gas condensate wells. The workflow can improve data utilization ratio, reduce the uncertainty of reserve estimation, avoid the development risk, optimize the development plan, and contribute the enhanced oil recovery in the late stage. It can be also used in other marine carbonate reservoirs. Recently, three thousand large-scale condensate gas fields have been discovered in the Ordovician carbonate reservoir of the Tazhong area, which is located in the middle part of the central uplift belt in the Tarim Basin〔1-2〕. However, the traditional material balance method for doing what is not applicable in this area due to many factors. First, the type of reservoirs is various, including cavity, fracture-vug, cleavage and matrix pore (dominant). Second, the flow mechanism is complicated, including seepage and conduit flow. Besides, fluid property is complex in nature, leading to low-, middle-, highcondensate and volatile gas reservoirs. Third, controllability is low during the development, the production model involves non-constant pressure and non-constant rate. Fourth, it is difficult to calculate the bottomhole flowing pressure due to the small difference between the formation pressure and the dew point pressure, there is the retrograde condensation phenomenon in formations, and multi-phase flows happen in the wellbore. Fifth, there are fewhydrostatic gradient data, and they do not decrease monotonically. Therefore, a great challenge facing developers is how to evaluate the dynamic production of complex carbonate gas condensate wells under the complex production status.
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Improving Safety & Reliability through Process Safety Management in Gas Handling facilities
Authors A. Eid Al-Adwani and V. Madhusudana Rao KapavarapuDuring the whole Facility Life Cycle of a Gas handling plant, Risk Management for protection of environment and communities and prevention of major hazards along with Asset Management are the key drivers for making the facility compliant with Health & Safety Regulations and Environmental issues and at the same time profitable economic and able to preserve asset value by improving the level of operational and process safety has become a crucial and challenging issue in a HSE perspective in Gas handling facilities. Process safety can be placed at the intersection of these independent but interrelated aspects and can be regarded as the key element for performing an integrated and comprehensive analysis capable to maximize plant effectiveness ensuring the best safety level, minimizing risks to safety and security and limiting at the same time downtime due to operational disruption or interruption, thus achieving consistency throughout the whole project life cycle. Therefore an effective process safety management demands a holistic and systematic approach for improving operational and process safety throughout the whole project life cycle from design and construction, through operation and maintenance, to decommissioning. In light of the above considerations a tool for process safety management has been elaborated and is hereafter described as a new structured approach of BAD ACTOR Identification in the facilities and its mitigation methods. Process Improvement approach was adopted in Kuwait Oil Company in Gas Management group and Gas Operations team and the similar culture was inculcated in to the operation employees to report all process incidents and BAD ACTORS. These BAD ACTOR events will be analyzed based on risk prioritization by conducting structure Risk analysis and Root cause analysis of various methods and recommendations will be implemented to avoid similar incidents to improve the reliability of the plant operations.
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Collapse Strength Study for the Solid Expandable Tubular
More LessThe paper summarized an experimental and theoretical study of the collapse resistant ability of solid expandable tubular (SET)after expansion, and the formula used to calculate the collapse strength of casing was modified to make it adaptable to the expandable tubular. One key limiting factor of the expandable tubular in its application in the open hole well to replace the casing is its postexpanded mechanical properties. The collapse strength of the expandable tubular after expansion was significantly compromised as the result of the comprehensive influence by the change of factors like the ovality, eccentricity and residual stress. In view of these problems, firstly full-scale expansion experiments were performed to examine all the impact of those factors; secondly the formula was modified based on the experimental data; thirdly the collapse experiments were carried out to test the strength of post-expanded tubulars as well as the accuracy of the modified formula. The results demonstrated that after large-scale plastic deformation, the dimension of the tubular changed dramatically as represented by the increase of eccentricity and ovality, the residual stress also appeared on both inside and outside surface of the tubular, the starting point of the collapse occurred at the position with the least wall thickness. The calculation results which reflected the average collapse strength of the tubular were larger than the actual experimental outcome but the error was kept well within 15%. We expect the research will contribute to the better understanding of the collapse resistant ability of post-expanded tubular and form the necessary technical basis for it future broad use.
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Nano-Ceramic Coatings- A Means of Enhancing Bit Life and Reducing Drill String Trips
Authors S. Sengupta and A. KumarDrilling bit is the main tool which performs the task of grinding and cutting through the formation. This causes cracking, spallation and delamination of the drilling bit and it needs to be replaced periodically depending upon the formation conditions. This replacement of the bit requires tripping the drill string and running it in again which causes loss of time. Also, a new bit has to be installed which causes monetary loss. Coating the bit with Nano-Ceramic coatings can help reduce the wear and tear significantly. Another promising fact is that these coatings don’t allow the metal substrate below to be affected. So, the worn out bit can be recoated with a fresh layer of Nano-Ceramic coatings and be reused. This paper shall go through the Nano-Ceramic crystalline structure, coating processes, testing mechanical properties (Young’s Modulus, Bond strength, Tensile strength) of the coatings and the comparison of mechanical properties of conventional and Nanostructured coatings. An application of this technology will be to use it for bits to drill highly abrasive formations like those formed by igneous rocks. The Nano-Ceramic coatings are made from an Al2O3-TiO2 Nano-Ceramic powder. This is applied on the bit surface via plasma coating method. The powder is partially melted to form grains of varying sizes. This lack of homogeneity is a major factor in enhancement of mechanical properties which will be explained further in the paper. There is a marked reduction in propagation of cracks as seen under SEM photographs. There is doubling of Bond strength as compared to conventional coatings.The toughness is about 2-4 times that of a conventional coating. This shall be further illustrated in the paper with help of graphs and images. This technology could lead to huge savings for operators as tripping frequency would be reduced. The replaceability of the bit also ensures savings for the operating company.
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Fracture Finite Difference Seismic Modelling
Authors M. Ferla and C. D‘AgostoThe objective of this study is to measure the seismic response of fluid filled fractures, trying to evaluate which acquisition survey parameters can better highlight this feature. The scope of fracture modelling is simulating the presence of a fracture system in the area of interest verifyin if it is detectable and describable by a 3D P-wave or PS-wave seismic data, for issues related to operative aspects but also for future support to the drilling activity. A system of aligned fractures can be described as an effective anisotropic medium when the dominant wavelength is long compared to the fracture scales. In order to model the behavior of seismic waves in fractured media, we can characterize the model with normal and tangential crack compliances, Coates and Schoenberg (1995). The main measurable effects on seismic data are the shear wave splitting and p-wave AVOaz anomalies. Shear-wave splitting due to the alignment of vertical cracks can be recognized by the polarization of the fast split shear-wave, which is usually parallel to the local strike of cracks and can be used to characterize fracture orientation. The time delay between fast and slow shear-waves is closely related to the intensity of crack-induced anisotropy in the medium (proportional to the fracture density). The main question to answer is if a 3D multicomponent survey can detect the travel time shift between parallel and perpendicular directions generated by the investigated formation. The second subject is to investigate the potentiality of fluid discrimination with PS waves but also PP waves. Modeled data is generated using elastic anisotropic finite difference code. The analogies between cracks systems and anisotropic media have been analyzed in order to infer interesting considerations about fractures characterization. The anisotropic parameters and the geophysical model have been assumed on the basis of inplace data measurements. The obtained results demonstrated the correlation between the seismic features and the fracture characteristics, such as crack density, fractures orientation, fluid content and AVO anomalies.
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Carbonate Rock Type Matrix, the Ultimate Rock Properties Catalogue
Authors O. Al-Farisi, H. Belhaj, S. Ghedan, S. Negahban, J. Gomes, F. Yammahi, M. Amr, H. Khamissa, K. Ibrahim and A. Al-ShamsiThe heterogeneity in carbonate rocks, made it hard for Geoscientists and Reservoir Engineers to define a universal classification methodology that is able to honour the critical reservoir static properties. Most classifications, like, lithofacies, capillarity and textural methods have based their rock typing concept on one or two static properties, then tried to find an analog to other static properties to cluster or group them, then worked to populate the rock types across the whole field. However, from field observations and experiences of utilizing these conventional techniques, it was obvious that they suffered from several gaps, like inability to have the properties analog consistent throughout the whole reservoir. Moreover, the groups or clusters have big dispersion that produced overlaps, and then theoretically they could not fully honour the physics and rock properties links. Therefore, in this study, rock typing is made to honour static properties all together through changing the classification concept to resolve the gaps of the traditional methodologies. The ultimate objective of all reservoir characterization and rock classification is to enable building geological and simulation models, with optimum honouring of rock properties. To achieve this objective, the established framework in this research is based on analyzing the effects of each of the rock properties on another and the value and impact that each can add to the models most critical parameters. By this technique, the gap of pore and pore-throat network is resolved through Multiple Properties Intersection. This Integrated Carbonate Rock Typing technique starts with capturing the heterogeneity of carbonate rock by generating matrix of core permeability, capillary pressure (end point, threshold pressure and Plateau), pore-throat size distribution and porosity. Then intersecting this matrix to construct weighted links between these properties and identify unique groups. Resulted classes are novel carbonate rock type classes that entered to feedback analysis node to explore and validate the logic of linked physics to tune the classes’ thresholds and assure no overlap between any of classification properties. Finally for utilizing this technique in non-cored wells, an analog with logging data is structured through novel permeability, capillary pressure and saturation function called the C-Function to be the replacement of the J-Function in Carbonate.
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Modeling of Spent - Acid Blockage Damage in Stimulated Gas Wells
More LessAqueous fluids introduced by different stimulation treatments cause water blockage in the near-wellbore region of wells. This water blockage acts the same as formation damage when the well is put back on production. One of the examples is when gas wells in carbonate reservoirs are acid-stimulated; the wormholes that propagate into the formations might be surrounded by a region of high water saturation created by the leakoff of spent acid. The spent-acid blockage damage could be severe, especially in lower permeability regions where capillary forces are relatively high. This paper presents a model that investigates the spent-acid damage in wormhole region of acid-stimulated gas wells. The phenomenon of spent-acid blockage was first investigated in the experimental study to identify the problem. A labscaled model was then developed to characterize the capillary pressure and relative permeability behavior by matching the results from the model to the experimental observation. We then extended the study to field-scale by approximating the wormhole as a long, slender half-ellipsoid centered in an ellipsoidal flow field. The simulations that focused on the displacement regime of spent acid recovery process were developed. These models were solved numerically to predict pressure behavior and spent acid distributions for the flow-back process. With the models, we studied the effects of several key factors, such as capillary pressure, relative permeability, and addition of additives, on the efficiency of spent acid recovery. The results show that common additives routinely added to acid systems may aid, or hinder, spent acid recovery, depending primarily on their effects on rock wettability. With the studies performed on the model developed, we provide recommendations for minimizing spent acid damage to gas well productivity.
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Solid Deposition in Gas Turbines of a Cogeneration Plant, Sumatra, Indonesia, Mechanism and Remediation
Authors R. Hwang, J. Iwamoto, P. Coughlan and D. KumboroA rapid build up of solid deposits occurred in the fuel system of gas turbines of the Duri Field Cogen plant and forced to shut down the plant frequently, which resulted in a great reduction in both electric power and steam output and hence curtailed tremendously the field production of heavy oil. A comprehensive study of the fuel gas delivery system and fuel gas quality was undertaken to determine the root cause of solid deposition. The results of the study show that the pale yellowish solids recovered from the fuel system are mixtures of elemental sulfur and wax. Both elemental sulfur and wax were derived from the fuel gas delivered to the plant where they were detected in the gas at trace levels (sub ppm). The occurrence of sulfur and wax deposition was somewhat surprising as the routine monitoring of the gas showed their levels were well within operation specifications all the time. Interpretation of composition data of numerous gas samples and solid deposits combined with operation conditions of gas turbines and gas phase chemistry provided insights of the solid deposition process. The problem was caused by the significant pressure drop encountered in the fuel gas delivery system of the turbines, which induced a measurable temperature drop and the associated phase changes of elemental sulfur and wax hydrocarbons from gas phase to condense phase leading to their deposition and turbine plugging. A remediation measure was developed and implemented.
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Study of Progressive Flow Profile of Multiphase (Oil-Water-Gas) Flow for Downhole Monitoring Applications
More LessComputational fluid dynamics (CFD) has been actively used to make flow profile predictions in downhole oil and gas environments. The flow in oil wells inherently consists of oil, water, and gas phases. Flow profile predictions are complicated by parameters such as fluid properties, flow velocities, area, and well inclination. A proper understanding of flow behavior under various operating conditions is critical when designing downhole equipment and flow metering applications. This paper presents case studies involving the three-phase flow of oil-water-gas in a downhole tubular. Phase distribution is analyzed for different compositions by varying the individual phase volume fractions. Various flow regimes, such as stratified flow, homogeneous flow, and bubbly flow, are studied individually as well as in their transition from one regime to another. The transition criteria were also studied. Extensive efforts were focused on understanding random bubble distribution, bubble breakup, bubble-relative movement, distortion, and diffusion in fluid flow with respect to flow variables. Finite volume phase distribution for oil vs. water is obtained as a function of time and distance (coherence) for multiphase flow in production tubulars. The effect of geometry changes with the objective of flow homogenization is also studied to enable the locations and numbers of monitoring devices to be fixed. CFD results were found to be comparable to single-phase analytical solutions. The examples and references included in the paper demonstrate the accuracy of the study results. The studies verify that an understanding of flow dynamics is essential to evaluate optimum configurations of the variables described. Advanced knowledge of flow characteristics enables engineers to deliver robust and maintenance-free sensing technology for use in a subterranean environment.
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Productivity Improvement Using Combination of Static and Dynamic Underbalanced Perforation in Tahe Oilfield, Tarim Basin, West China
Authors L. Fuqiang, L. Lian, L. Li, H. Yong and Z. GangIn concern with the skin factor value, the key significant components which do not directly depend on the nature of the reservoir properties are drilling/ completion fluid invasion damage and perforating induced damage. The oil & gas industry has been tried to eliminate the fluid invasion issue by applied deep penetration perforating to bypass the invasion zone and reach un-invaded reservoir. Lots of experiences and lab analysis shows that perforation performance is not meet the expectation of the productivity because of the perforation induced damage. As for now, static underbalanced perforation has been recognized by industry as one of the method to obtain clean perforation tunnel. However, static underbalanced perforation method is not always giving the expected productivity result. Experiments showed that the cleanup of the perforation tunnel was not totally dominated by the static under-balance pressure but also the transient pressure during the first 100 milliseconds of perforation or dynamic under-balance. The dynamic underbalance can be obtained by creating an instantaneous drop in pressure around the guns during perforating. The combination of static and dynamic underbalanced perforation with deep penetration charges which be able to bypass an invasion zone, can create a clean tunnel, and significantly reduce the post-perforating damage by killing fluid, and finally maximized the productivity. This combination of the static and dynamic under balance method has been applied in Tahe Oilfield. Tahe oilfield is located in Tarim basin with reservoir horizon depth of 4100m-4600m,temperature of 94-103
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An Integrated Model for Selecting The Best Fuel to Develop in The Value Chain of Natural Gas
Authors A. Mousaei, A.A. Ghadirian and M.A. HatefiA value chain is a series of events that takes a raw material and with each step adds value to it. Global interest in the application of natural gas in production and transportation has grown dramatically, representing a long-term, low-cost, domestic, secure, etc. alternative to petroleum-based fuels. Many technological solutions are currently considered on the market or in development that address the challenge and opportunity of natural gas. In this paper, an integrated model is introduced for selecting the best fuel to develop in the value chain of natural gas through the four options: Compressed Natural Gas (CNG), Liquefied Natural Gas (LNG), Dimethyl Ether (DME) and Gas-To-Liquids (GTL). The presented model uses the Multiple Attribute Decision-making (MADM) techniques to select the best fuel in the value chain of natural gas based on the criteria such as market situations, technology available and transportation infrastructure. The model recommends some key guidelines for two branches of countries i.e. those have natural gas resources and the others. We believe that applying the proposed model helps the oil & gas / energy ministries in most effective and productive manner dealing with his complicated fuel-related production and transportation decision-making situations.
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Anisotropic Waveform Inversion with Well Constraints
Authors C. Wang, D. Yingst, J. Leveille and R. BloorThe term, "Waveform inversion" (WFI), refers to a collection of techniques that use the information from seismic data to derive high-fidelity earth models for seismic imaging. The attractiveness of WFI lies mainly in its lack of approximations, at least in a theoretical sense, in contrast to other model determination techniques such as semblance or tomography. However, a whole raft of approximations must be made to make the technique viable with today's computing technology and restrictions of seismic acquisition. These are collectively referred to as "waveform inversion strategies" and in this paper we mainly discuss regularization and preconditioning strategies. Because the wavefields need to be accurately modeled to represent the kinematics of all the waves during WFI iterations, the effects of anisotropy often help to improve WFI results. In this paper, forward modeling and its adjoint computation are based on acoustic wave equations in vertical transversely isotropic (VTI) media. We introduce a multi-parameter inversion for P-wave velocity and anisotropy parameters. WFI is a highly nonlinear, ill-posed problem. We introduce additional information and turn the unconstrained optimization problem into a constrained optimization problem in order to reduce the ill-posedness. The geophysics of the problem leads to appropriate constraints, such as restriction of model parameters, or information from well logs. In this paper, we use well logs as constraints and solve the problem using the augmented Lagrangian method (ALM), a mathematical method that replaces a constrained optimization problem by a series of unconstrained problems. The ALM with well constraints aims at preserving velocity characteristics from well logs and providing us with more reliable velocity updates. This paper presents the acoustic anisotropic WFI implementation using ALM with well constraints. It also discusses practical strategies for regularization and preconditioning and their influences on the models that are obtained from WFI. We illustrate these approaches on a 2D synthetic Marmousi example and another application to 3D VSO OBC data from the Green Canyon area of the Gulf of Mexico. From the results, we show that multi-parameter VTI WFI with ALM provides us with more useful and reliable model updates. To further evaluate our WFI results, we also compare offset gathers and RTM images and illustrate their significant improvements using updated models generated from WFI.
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How Ball Materials Impact the Performance of Open Hole Fracturing Systems
Authors J. Baihly, J. Johnson, G. Melenyzer and I. Avilesmpletions rely on a sliding sleeve activated by a ball dropped from surface. Each ball travels the length of the lateral well to its intended operational depth, at which it meets a mated seat and isolates the wellbore below. Once the ball is in position, the sliding sleeve opens via the hydraulic force on the ball and seat, allowing a fracturing stage to commence. This dual function of the ball—activation and sealing—is of extreme importance for the stimulation treatment process. If the ball fails, it will result in bypassed pay zones and unintentional refracturing of previously stimulated zones. Although sometimes surface pressures can be used to infer ball behavior, often the pressure signals observed at surface cannot guarantee successful ball performance. This paper will present an extensive study of ball performance under pressure for the most common ball materials in the industry. Phenolic, composite and metal alloy materials were explored with the pros and cons for each investigated. In particular three main areas were analyzed: 1) molding, layering and extrusion of material versus inconsistencies in ball performance; 2) ball deformation at high pressure versus pressure required to bring the ball off seat; and 3) comparison of the performance of phenolic, composite and metal alloy materials for ball fabrication and their performance at high temperature. Manufacturing variability is also explored on this paper. The impact on the manufacturing process on the performance of balls made of the same material is presented by means of laboratory experimentation. The conclusions from this paper provide operators the necessary information to consider when making completion and ball material decisions in their field operations. In particular, the results of this testing may illuminate some previously unexplainable occurrences in graduated ball sliding-sleeve systems. This testing clarified that not all fracturing balls pumped in horizontal wells perform equivalently under wellbore fracture conditions.
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First Successful Application of an Environment Friendly Fracturing Fluid During On-The-Fly Proppant Fracturing
Authors M. Al-Ghazal, S. Al-Driweesh and F. Al-ShammariWith the increasing demand for natural gas, fracturing fluid technology needs to develop to enable optimized well completion operations with minimum ecological impact. The recent development of environmentally friendly polymer-free fracturing fluids — with superior operational performance — represents a major technological advance in the petroleum industry. The use of these new fluids during fracturing operations has the following benefits: minimized environmental footprint and formation damage, operational efficiency and simplicity, and maximized fracture conductivity. This paper discusses the first successful deployment, of an environmentally friendly polymer-free fracturing fluid, during on-the-fly proppant fracturing in Saudi Arabia. Also, the paper discusses the optimum layout of the fracturing equipment used during the job execution. The fluid was used to fracture a gas zone located between two water zones. Therefore, one of the main objectives of the treatment was to control the height of the fracture to not break through and contaminate the water-bearing zones. In addition, the fluid exhibited a low friction pressure and excellent proppant-carrying capacity. Moreover, the overall cost of this fracturing operation is in line with conventional, polymer-based fluid fracturing approaches. Evaluation of the post-treatment results demonstrated the following: very positive well productivity, improved fracture geometry (longer fractures with better height containment), and faster fracture cleanup time.
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The Role of Underground Storage in Large Natural Gas Production Operation
Authors M. Hoagie, G. Amorer, X. Wang and M.J. EconomidesUnderground natural gas storage has been used extensively in countries with large natural gas demand. Although much of the storage and withdrawal have been associated with seasonality, storage is becoming essential in an integrated natural gas management. It is particularly important in large operations, such as liquefied natural gas (LNG), where the total production rate must be maintained irrespective of the producing field day-to-day capacity. Natural gas storage capacity is affected by reservoir volume and tolerable pressure (to avoid fracturing) and injection or production rates that are affected by reservoir permeability, natural reservoir drive mechanism, well completion/stimulation, and the impact of cyclical losses. We present here a new sequence of calculations and estimations demonstrating salient elements of this practice: • Maximum capacity estimation with a new type of graphical construction, blending concepts of the classical p/Z vs. cumulative recovery straight line in natural gas production. • Prediction of withdrawal rates and time, constrained by decreasing storage pressure. • Determination of maximum or sustainable withdrawal rate for a period of time. In all cases, the injecting and producing wells are hydraulically fractured. The hydraulic fractures are designed for the withdrawal rate. Thus, the required number of wells is determined. These concepts are applied to a depleted natural gas field with an average pay of 33 ft and a permeability of 45 md. Forecasts of injection or production rates, cumulative storage or withdrawal, and pressure buildup or decline are presented as functions of time. The purpose of this case study is to sustain an LNG liquefaction operation for a specified period of time by employing underground natural gas storage.
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A New Model to Predict Average Pressure Difference of Liquid Droplet in Gas Well
Authors Z. Hai-Quan, L. Zhong-Neng, L. Tong, L. Kai and R. YongThe distribution of droplet surface pressure is uneven under the action of high velocity gas streams in gas wells, and there exists a pressure difference which leads to droplet deformation before and after the droplet. Moreover, it affects the critical liquid carrying rate. The pressure difference prediction model must be determined, because of the existing one lacking theoretical basis. Based on the droplet surface pressure distribution in high velocity gas streams, a new model is established to predict the average differential pressure of droplets. Compared with the new differential pressure prediction results, the existing pressure difference prediction results overvalued by 46.0%.This article also improves four gas-well critical liquid carrying models using the proposed pressure difference prediction model, and compares with the original one. The result indicates that the critical velocity of the original models is undervalued by 10% or so, due to the overestimate to the pressure difference.
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