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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
101 - 120 of 581 results
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Wellbore Stability Evaluation Guideline For Reducing Non-Productive Time
More LessWellbore instability is one of the most critical challenges affecting drilling and production. Borehole instability in both shale and sand formations, hole collapse, lost circulation, stuck pipe, sanding, and other related well failures can be avoided by meticulous and careful design of drilling plan, specially by determining the critical mud weights and mud fluid components which will provide sufficient support for the wellbore during drilling operation. This paper presents a systematic program and guideline of comprehensive geomechanics investigation and evaluation that includes drilling and log data analysis for rock strength and earth stress model construction, stress regime influence, laboratory triaxial stress-strain tests on well core samples considering bedding plane inclination effects, failure criterion consideration, and optimum mud-weight (MW) window for secure and stable well drilling. The continuous well production can also cause problems for in-field drilling as the severe pressure depletion and reservoir compaction would inevitably induce significant reduction in stresses and formation fracture gradient both inside the reservoir and significantly upward into the caprock formations depending on the reservoir/formation stiffness contrast, reservoir size, thickness and depth, etc. This paper addresses those issues with the optimum MW reexamined and recalculated based on the largely altered in-situ stresses and wellbore strengthening application if necessary. This paper will describe theories, some issues in wellbore stability work, discuss some uncertainties from authors’ experience, lessons learned and guidelines for wellbore stability evaluation.
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Application of Low Pressure System at Balingian, Sarawak Brown Field; Candidate Selection and BY Field Case Study
Authors M. Syahezat Ismail and N. HamzaBayan (BY) is a brown field located in Sarawak region with over 25 years of production. Declining trend in field production resulting from rapidly declining reservoir pressure and increasing water production has prompted aggressive production enhancement activities to arrest further decline. Conventional gas lift method has been widely applied across the field and has provided reliable means of artificial lift to sustain production. However, wells with very low reservoir pressure were not able to sustain production even with gas lift due to the back pressure experienced in the production system. Low Pressure System (LPS) were implemented in two (2) out of four (4) drilling platforms in BY to sustain and increase the field production, reactivate idle wells and to manage the back pressure for the whole production system. Experience gathered from this implementation enable us to improve the candidate selection process and to share potential limitation imposed by the LPS system to operation. Actual BY LPS performance is shown here to illustrate the proven success in increasing the field production and unlocking some of BY reserves. The change in the production trend of well’s producing in current production system and after being tied to LPS will show the total achieved production gain which in BY case amounted to more than 1.5 million barrels in 4 years of operation.
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A Successful Subsalt Exploration Example of M Block in The Eastern Margin of Precaspian Basin
Authors Zhen Wang, Junzhang Zheng, Yankun Wang and Man LuoM block in eastern margin of Precaspian Basin is the first CNPC ’s risk exploration project in Central Asia & Russia, which has been prospected by many companies and no discovery was found. The main exploration difficulties are subsalt trap recognition’s trouble caused by salt domes with giant thickness (greater than 1000m) which lead to subsalt target stratum’s pull-up and false faults in the Permian and strong heterogeneous reservoir prediction in carbonate reservoir buried near 4000m. Technology was developed based on the difficulties, in the aspect of subsalt structural recognition, fine interpretation by multidisplay methods, salt domes’ margin identification using boundary detecting technique, time-depth conversion methods of raytracing procedure, forward modeling examining velocity field’s precision, vertical seismic profiling (VSP) detecting local structural shape, palaeotectonic restoration analyzing trap’s origin, prestack depth migration verifying trap’s validation, salt dome’s influence was wiped out continuously and strata’s real shape was resumed which leads to the increase of drilling success ratio. In the aspect of carbonate reservoir prediction, favorable reservoir zones in Carboniferous strata were outlined based on the study of logging assessment, sequence stratigraphy, sedimentary facies, seismic inversion, fracture and petroleum detection, attribute analysis. At the same time, REI(reservoir evaluation index) and CI(cave index) indexes were initiated, and carbonate reservoir’s logging assessment standard in this block was established that improves reservoir prediction’s precision. In the aspect of comprehensive evaluation, 3 structural accumulating belts were divided after the study of reservoir types, which are west structural belt, central structural belt and east structural belt. The different belts’ play was evaluated synthetically. The main and potential play was pointed out in different belts. The regular patterns about subsalt carbonate accumulating were generalized. Middle ramp region should be break through first is our bulk exploration deployment clue, and a big field with more than a hundred million tons reserves was discovered which is the biggest subaerial discovery since the Kazakhstan being self-governed and guarantees the abundant supply for the Central Asian pipeline.
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Sichuan Shale Gas Microseismic Monitoring: Acquisition, Processing, and Integrated Analyses
The ability to estimate the stimulated reservoir volume and to enhance the effectiveness of hydraulic fracturing operation is fundamental in field development planning and critical to optimizing well completion in unconventional gas exploration and production. Microseismic Monitoring (MSM) survey provides essential observations study how induced rock volume responds seismically under field hydraulic fracture stimulation. Recent advanced microseismic technology with further development can provide real-time monitoring and interpretation which will improve hydraulic fracturing efficiency and better EUR, stop induced fracture development toward fault zones, and avoid connecting water-bearing layers. Advanced processing can enhance weaker microseismic signal, which provides a more complete Microseismically-Stimulated Reservoir Volume (M-SRV). M-SRV is essential to build the 3D understanding of the induced fracture network under various stimulation designs in volumes and in patterns from each fracturing stage.
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Modelling the Transient Behaviors of the Kinetics in the Transesterification of Palm Oils Reveals Prospects for Customization of Esters for Drilling Fluids Formulation
By E.O. OkekeThis paper discusses the prospects for customizing esters derived from palm oils as part of the first phase of a study to develop new drilling fluids. This phase evaluates the feasibility and prospects for customizing such esters in order to fully define experiments and all analytical conditions for realizing the objectives of the entire study. Published studies in transesterification show products from various vegetable oils for different applications including biodiesel production. Vegetable Oils consist of triglycerides (TG) 90 - 98 % by weight, small diglycerides (DG) and monoglycerides (MG), while palm oil contains TG 95.7%, DG 3.7%, and MG 0.6%. Transesterification of vegetable oils with alcohol is characterized by multiple consecutive and reversible reactions. TG is converted stepwise to DG, MG and finally glycerol (GL). We are particularly interested in palm oils (developed in large plantations in Nigeria). ASPEN HYSYS 7.3 was used to model the non acid catalyzed transesterification involving three reactions each with methanol for conversion of TG, DG and MG under steady state and transient conditions in a CSTR at varied reaction conditions and time to produce varied esters properties. Results from the model show prospects for customizing esters derived from the transesterification of palm oils and realizing their application in drilling fluids formulation.
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Knowledge Management in Engineering Activities of an Operating Company
Authors G. DiLiddo, G. Gabetta, F. Ponti, P. Cavassi and P. FassinaA better Management of Knowledge is an actual need in the Oil&Gas industry. In the past years, as a matter of fact, the amount of information available to engineers and scientists increased exponentially thanks to developments of the ICT tools making therefore harder to handle it. On the other hand, industry practice is to keep the plant running, implying that decisions have to be made quickly and time is short to collect and examine all the possible information. A solution to these challenges is Knowledge Management, which is defined as the ensemble of processes that allow to capture, validate, consolidate, archive, re-use and diffuse knowledge in order to improve both business processes and innovation processes. To make it happen, new ICT tools and mindsets need to be developed and exploited. In Eni E&P Division, a Knowledge Management System (KMS) is operating since 2004 with the aim at facilitating and speeding-up the sharing of best practices, lessons learned and other Know How across the organisation; several ICT tools are employed, such as forums, mailing lists, SharePoint websites, webinars etc. The KMS is based on several Communities of Practice, which have the aim of conveying technical debate transversally to different disciplines and to the entire eni group, which is heterogeneous due to geographical location, culture, industrial sectors and discipline involved. The resulting interactions, moreover, bring the advantage of making explicit (and durable) all the personal knowledge of the members that would otherwise got lost due to turnover and distance among the employees. Taking into account the results of the first few years of implementation of the KM system in the engineering area, this paper will summarize the successes and lessons learned during the operating life of the Communities, to trace a road map for the future work.
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Seismic Guided Drilling: Near Real Time 3D Updating of Subsurface Images and Pore Pressure Model
More LessSeismic guided drilling (SGD) is a workflow that uses drilling information from a well being drilled and existing surface seismic data plus offset well information, to recalibrate and update the existing 3D earth model, including seismic image, pore pressure, fracture gradient, and geological hazards in order to reduce drilling uncertainty and mitigate drilling risk ahead of bit. The modern practices in drilling heavily rely on the predrill earth models. The predrill models often are not precise due to the inherent non-uniqueness in our remote sensing techniques. While LWD/SWD and WL provide useful information along the borehole, they offer little understanding about the rock property ahead of bit. SGD is such a technology that constantly improves the 3D earth model ahead of the bit through the integration of current well measurements with existing surface seismic data, with a turnaround time on the order of 24 hours. It not only corrects the model error behind the bit but also improve predictions ahead of the bit. The lack of adequate technologies, measurements, and turnaround time limitations, has made this type of optimum utilization/integration of seismic data and well data impractical until now. Recent developments in model building, rapid and accurate imaging technologies, and the availability of new well measurements, aided with modern engineering and computation, have made this optimum combination a reality. SGD has been used in several high-profile deep water HPHT wells worldwide with considerable successes. The technology is especially valuable in areas of low exploration activity or high geological complexity. The paper focuses on illustrating the concept of SGD technology and presenting a field example in the Gulf of Mexico, USA.
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Qualification Testing of Large Bore, HP Tubing Retrievable Safety Valves for Gas Wells
Authors M.A. Ali and A.S. AbdulrahmanOver the past decade, the role of natural gas has become increasingly important in fulfilling the ever-increasing energy needs of the world. Natural Gas has not only become an integral part of the world’s energy portfolio but also offers a cleaner and more efficient fuel to help reduce carbon emissions when compared to oil. Recently, Saudi Aramco has made three major offshore, high pressure, non-associated gas discoveries. A large bore completion design was selected for these fields in order to bring these discoveries on line quickly and cost effectively. The surface controlled, sub-surface safety valve is a critical component of the asset integrity management program for these gas wells. In order to meet the requirements of completion design and reservoir pressure, the world’s first 9-5/8in 10,000psi rated TRSSSV were developed tested and qualified for these developments. As part of qualification testing, high rate slam closure testing of the TRSSSV was carried out at the Southwest Research Institute and at GL Nobel Denton facilities. The objective of the tests was to ensure that TRSSSV closes, seals and continues functioning after a slam at the highest anticipated flow velocity in the wells. Additionally, slam test results were used to design surface and subsurface components that are required to operate the TRSSSV and must be capable of withstanding the shock load produced by a slam closure. Two leading completion companies were selected to develop and provide the TRSSSVs for these projects. Both designs suffered initial failures, required significant modification, and underwent extensive tests before the final designs were successfully tested. This paper discusses the basis of design, test criterion, results and lessons learned from the slam testing of the world’s first 9-5/8in, 10,000 psi rated TRSSSV. The paper also provides an overview of the two test facilities used, their limitations, and recommendations for future tests.
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An Experimental Study on Mitigation of Oil Well Cement Gas Permeability
Authors M.H. Ozyurtkan, G. Altun, I. Metin Mihcakan and U. SerpenPermeability development within and around the cement, placed in the casing-hole annulus in oil and gas wells, is a frequently encountered worldwide problem that might lead to various adverse economic and, possibly, catastrophic consequences. The resultant loss of hydrocarbon production and, sometimes, the wells constitutes the major part of the adverse economic impact. The loss of wells, in turn, might lead to severe environmental pollution and most importantly the loss of lives. Sustained casing pressure (SCP,) described as the pressure buildup due to flow through the permeable cement matrix or the micro annulus developed around the cement, had been experienced by about sixty percent of the wells producing oil and/or gas in the Gulf of Mexico, according to the literature. Although various methods are used to prevent the problem, there is no widely accepted universal method by the industry. Currently, the problem is attempted to be mitigated using distinct methods applied either during the cementing operations or after the problem is detected. The present study is an experimental investigation for the prevention of permeability development within and around the set cement at ambient conditions. A natural magnesium complex with carbonate, coded ARI, is used the first time ever as a cement additive to achieve desired prevention. Gas permeability measurements are conducted on the samples of cements of 19 different compositions, at the end of the successive curing periods up to 28 days. ARI containing cement samples are found to develope an impermeable matrix to gas flow and to exhibit no shrinkage in volume during setting. The performance of ARI as a cement additive is also investigated in the presence of other commonly used cement additives, e.g. friction reducer and fluid loss controlling agents.
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Well Failure Detection for Rod Pump Artificial Lift System through Pattern Recognition
More LessWell Failure Detection for Rod Pump Artificial Lift System through Pattern Recognition
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Fundamental Approaches to Dolomitization and Carbonate Diagenesis in Different Hydrogeological Systems and the Impact on Reservoir Quality Distribution
Authors Y. Xiao, F.F. Whitaker, A.B. Al-Helal, S. Stafford, E. Gomez-Rivas and S. GuidryThe accurate prediction of the geometry of subsurface dolomite geobodies, their connectivity, and the distribution of reservoir properties is a fundamental challenge in carbonate reservoir characterization. Reactive Transport Models (RTM) couple geochemical reactions with fluid flow to facilitate both 2D and 3D quantitative, process-based investigations of dolomitization and related carbonate diagenetic reactions. The paper will highlight new results and key conclusions from simulations of dolomitization mechanisms in four different hydro-geological systems: 1) Brine reflux, 2) Mixing zone and sub mixing zone, 3) Geothermal circulation and 4) Fault controlled hydrothermal circulation. Simulations provide new insights on the spatial distribution and dynamic behavior of: Geometry and distribution of dolomite bodies generated by different styles of subsurface fluid flow and their dynamic interactions; Regional versus local controls on dolomite occurrence and connectivity; Sensitivity and hierarchy of geological controlling parameters; Spatial and temporal relationships between dolomitization and associated diagenetic minerals including anhydrite cements and Mississippi Valley Type (MVT) mineralization; Effect of hydrothermal fluid induced dolomite recrystallization and anhydrite dissolution; Criteria to help identify the distribution of reservoir quality including high permeability dolomite “sweet spots”. When integrated with conventional subsurface data and stratigraphic, geochemical, and structural framework, Reactive Transport Models of dolomitization provide fundamental and robust predictive concepts and reservoir quality models for exploration and new / mature field developments. In particular, the state-of-the-art simulations allow the analysis and 3D visualization of dolomite body spatial and temporal evolution that can translate into alternative “process-based” well correlation methods and strategies for populating diagenetic bodies and their petrophysical properties in geological models for reservoir flow simulations.
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Rock Mechanical Properties of Shale Gas Reservoir and Their Influences on Hydraulic Fracture
More LessEach shale gas play is unique and the stimulation and completion method should be determined based on individual attributes. Selecting the completion style for an emerging shale play should begin in the laboratory rather than copy successful cases. An understanding of the rock mechanical properties is essential to help understand how the shale reservoir should be completed. We conducted triaxial compression tests for specimens from North America and South China. The failure modes and mechanical behaviors are analyzed. A new method combines rock mechanical properties and mineralogy to quantify the brittleness was derived and the practical use is demonstrated afterwards. Natural fracture analysis from core and borehole image are conducted and potentially active fractures, which could be most important hydraulic conduits and another index of the fracability, are identified through a three-dimensional Mohr representational method. The results of this study revealed that black shales are usually more brittle than imagined. Splitting and splitting-shear hybrid failure modes are the main failure modes under low confining pressures, while shear failure modes predominate under higher pressures. Types of shale, burial depth, coring direction and confining pressures are all affecting the mechanical behavior of specimens. The brittleness characterization of shale samples from China is similar to that from America. Compared with North America, shale from South China has higher strength and Young’s modulus, while lower Poisson’s ratio. A systematic approach of designing completion and stimulation is proposed based on brittleness, closure stress and hydraulic fracture width. The analyzing results from two shale gas wells verified the value of this method. Brittleness calculating results allied well with initial production of these wells, indicating good application prospects. Calculation of strength properties, closure stress and fracture width can be practical useful in selecting and designing stimulation measures.
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Fracture Optimization Applying a Novel Traceable Proppant and a Refined Mechanical Earth Model in the Congo Onshore
Authors R. Perfetto, P. Saldungaray, F. Martocchia, R. L. Ceccarelli, R. Lorefice, F. Rinaldi, L. Tealdi and P. DalmassoFracture stimulation has been adopted as an integral part of the completion in the M’Boundi field given the results achieved in enhancing well productivity, as well as the positive impact realized on field development economics. The fracturing process has been optimized over the years through improved reservoir understanding and ensuing implementation of technologies to address the uncovered challenges. Changes to the fracturing fluid formulation to prevent damaging the water sensitive reservoir rock, as well as modified proppant schedules to mitigate proppant embedment are examples of this improvement process. This paper describes the successful ongoing process of optimizing hydraulic fracturing designs in M’Boundi field. By applying an integrated approach combining various technologies, it was possible to better understand fracture propagation and coverage of the target reservoir. Implementation of a novel non-radioactive traceable proppant allowed accurate frac height measurement at the wellbore. When combined with rocks mechanics derived from sonic logs it led to redefining the mechanical earth model and ultimately the completion and fracturing strategy in the field. The process will be illustrated with examples from a 3-well campaign recently executed onshore Congo.
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Determining Coefficient of Quadratic Term in Forchheimer Equation
More LessForchheimer equation takes non-Darcy flow effect into account in the event of high flow velocity in porous media. Its application requires both permeability, which is in linear term, and Beta factor, which is in quadratic term. Permeability and Beta factor are determined by rock type, textural of rock, effective porosity, pore throat size, geometry of the pore, and connection and distribution of pores. Beta factor comes into play when the fluid flow rate is high and the flow rate deviates from Darcy’s law. Non-Darcy flow is described by Forchheimer equation. Usually the coefficient of non-Darcy flow term is hard to be determined. Existing approaches are core measurement and empirical correlations. To the best of our knowledge there is no theoretical equation available. To get an accurate estimation of flow rate or pressure drop in the reservoir, we need a method that has solid theoretical basis. The deficiency triggered our study. Starting from multiple-capillary tubes concept, we derived a rigorous relationship between pores geometry and pressure drop required for fluid flow through the pores. Through this correlation pressure drop can be calculated from known pores geometry. Since pores geometry can be often obtained from lab experiment or well logging, the new correlation also provides a unique approach to quantify the coefficient of quadratic term in Forchheimer equation. In this study we developed a governing equation through a rigorous theoretical derivation. With this equation the non-Darcy flow coefficient in Forchheimer equation can be calculated. The required input data for the new equation are readily obtained from well log interpretation. The new equation is a powerful tool in the event of no experimental measured non-Darcy flow coefficient available. It eliminates the errors or the arbitrary content in the empirical correlations.
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Using a Novel Spacer and Ultralow Density Cement System to Control Lost Circulation in Coalbed Methane (CBM) Wells
More LessCoalbed methane (CBM) is one of the major clean-burning gas resources. Development and utilization of CBM can increase the energy supply, improve coal mine safety, and protect the global environment. The southern Qinshui basin of China is rich in coalbed methane; it is the first area that obtained good results in the commercial development of CBM in China. However, lost circulation is a common problem during cementing through the fractured coal-seams known as cleats. These cleats form an interconnected fracture network and this allows cement slurry to loss through the coal-seams during cementing operations. Cleats are often wide enough to accept cement slurry, not just cement slurry filtrate. Hence, simply reducing slurry density does not ensure a good cement job. Preventing cement slurry loss to coal-seams while cementing production casing is a major challenge. To solve lost circulation problem across coal formations, an innovative hydrophilic-fiber-based spacer fluid and ultralow density cement slurries with density of 0.95-1.20 g/cm3 have been formulated. Laboratory tests have verified the effectiveness of hydrophilic-fiber-based spacer fluid in plugging these cleats of coal-seams. The ultralow density cement slurries exhibite favorable properties. These test results are confirmed by the good field application results obtained in southern Qinshui basin. Fourteen CBM wells have been successfully cemented using the novel spacer fluid and the ultralow density cement slurries. The combined application of the hydrophilic-fiber-based spacer fluid and the ultralow density cement slurry system is able to successfully combate the lost circulation problem in CBM wells, and provides better zonal isolation as well. This paper provides details about the slurry design and field application, and also presents the cement bond evaluations that verify the conclusions.
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Assessing Unconventional Resources Using an Integrated Petroleum Systems Approach
Authors A. Shankar Roy, Alexander Neber and Zailani Abdul KadirPetroleum system modeling has matured in the past few years and is now a valuable component in conventional exploration. It has become best practice to mitigate risks by using petroleum system modeling to predict the presence, types, and volumes of hydrocarbons in prospective areas or structures before drilling. An adaptation of this methodology has been successfully applied to unconventional resource plays. Petroleum system modeling may be applied to predict: the type and quantity of hydrocarbon remaining in the source rock, proportion of adsorbed gas, porosity, and geomechanical properties of potential unconventional reservoirs. A new methodology has been developed to integrate trap, reservoir, charge, seal, and other risk (sub-) elements to evaluate play risk. Chance-of-success (COS) maps are created by transforming the physical propertiy maps to maps with probability units. As data, interpretations and related COS maps are in the same software system, the evaluation can be kept alive and dynamic as new data interpretations become available. Within the same application, prospect COS can be evaluated using a consistent approach This paper illustrates this methodology using examples from shale plays in North America, data-rich plays from the North Slope of Alaska and data-poor plays that are more representative of many Asia-Pacific basins from the north-eastern and southern regions of the United States. The examples demonstrate the application of the methodology in both frontier and mature areas, either in quick data-room reviews or for delineating prospects.
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Hawiyah Gas Plant Alarm Rationalization and Controller Performance Monitoring
More LessIn order to improve the plant and operation efficiency and reliability, HGP established a consistent and standard methodology for the development, implementation, and modification of process and system alarms. In addition, this methodology serves as guideline to monitor, fix and report bad actors in alarms and PID controllers. The task involves a comprehensive study to the entire plant alarms database including settings, grouping, priorities, philosophy and configuration. In addition, this task will ensure the continuity of PID controllers monitoring to ensure that all of the plant PID controllers are in auto and they are maintaining their set point. Succeeding to achieve this will ensure the optimum performance and efficiency and ensure more vigilant operation. HGP succeeded to bring the controller in auto to above 90% and a full alarms rationalization study was conducted to bring the alarms level to the international KPIs. The paper will start with providing basic background about essential definition including the alarms, alarm rationalization and controller performance monitoring. Thin, the paper will address the importance of the subject and the need of the improvement. As there are many recent studies indicates that missing critical alarms lead to fatal insidents and major damages to different facilities. In addition, many of the plants upset and changes could have been avoided if good alarming system is in place. Beside all of this, the paper will address the importance of the plant controllers’ automation as having these valves on auto will assure having the targeted product with the best possible efficiency.
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Successful Implementation of Fiber-Laden Fluid for Hydraulic Fracturing of Jurassic Formations in Western Siberia
Authors R. Kayumov, Aleksey Borisenko, Olesya Levanyuk, Irina Savelyeva and Sergey EmelyanovThe Urnenskoe field is located in the Tyumen region, Western Siberia. The main production target is the J1 formation belonging to the upper Jurassic Vasyugansk suite. Subsurface geology of the Urnenskoe field features the lithological heterogeneity of the J1 formation with high- and low-permeability interlayers and considerable petroleum reserves in upper low-permeability formation intervals. Oil and water have highly different viscosities permitting rapid water breakthrough into the formation. The first hydraulic fracturing operations were carried out at the Urnenskoe field in 2010. Because there are rich oilsaturated zones in the low-permeability upper zone of the reservoir, the properties of the fracturing fluid to transport proppant and its ability to prevent settling during both the pumping and when the fracture is closing are decisive for the well productivity after the fracturing operation. Fracturing fluid with degradable fibers was selected to achieve these properties during hydraulic fracturing. The fibers create a reinforcing net within the fracturing fluid with proppant and mechanically assist the transportation and suspension of the proppant grains. The temperature decomposes the fibers when the fracture is closed. In addition, the fibers allow lowering the polymer concentration in the fracturing fluid, thus enabling control of the fracture vertical growth and decreasing proppant pack damage. Since there are no all-season roads and it is difficult to approach the Urnenskoe field in the summer, there was no fracturing fleet capable of performing an operation utilizing the fluid with degradable fibers in July 2011. Therefore, 7 conventional fracturing operations were performed; these can be used to compare the effectiveness of conventional fracturing with another 23 operations in which the fibers were used. These operations revealed that the wells in which the fibers were used had a dimensionless productivity index that was 33% higher, and this effect remained stable. Also, for the wells with the fiber application, the average cumulative oil production for 5 months was 2,245 tons higher (recalculated for one well). These results confirm the effectiveness of hydraulic fracturing with degradable fibers in the Urnenskoe field. The successful experience of using hydraulic fracturing with degradable fibers at the Urnenskoe field, laboratory tests of the fiber-laden fluid, analysis of well productivity, and particular applications of the technology provide information to guide further optimization. In addition, the technology has been applied in the Jurassic formations of the neighboring Ust-Tegusskoe field, where a considerable productivity gain was achieved compared with the conventional fracturing operations.
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Mitigation of Deepwater Shallow Hazards with Simplified Cement System: South China Sea Case Study
Authors T.B. Ellis, E. Paul and R. AcordaCementing is one of the most critical steps in the well construction phase. Qualified cement integrity is considered a barrier to inhibit fluid migration to surface. For conventional wells, cement in addition to barriers such as BOPs (Blow Out Preventers), fluid hydrostatic pressure, and mechanical methods are used to ensure fluid migration is inhibited. For top-hole sections of deepwater exploration wells however, cementing is your only barrier to mitigate uncontrolled fluid flow to the seabed. During the top-hole operations (typically 36-in. and 26-in. hole sections), the bore hole is drilled without a riser and returns are taken to seabed. This creates difficultly in controlling shallow hazards such as gas hydrates and shallow water flow because the well cannot be killed using conventional methods. To assure mitigation of shallow hazards, an emphasis is made on achieving short transition times for cement designs. For South China Sea operations, it is common practice to incorporate cenospheres (dry blended lightweight additive) into the cement design to ensure suitable properties are achieved. However, the use of cenospheres requires blending onshore and excess blends to be shipped offshore for contingency purposes. Although required slurry properties can be achieved with cenospheres; logistical issues, left over disposal concerns, costs, and low cenosphere pressure ratings create a complex operation. In addition, cement systems should be designed to incorporate loss of lightweight material during transfer offshore, and must account for higher down-hole densities due to crushing of lightweight cenospheres. All of these processes require great emphasis on Quality Assurance / Quality Control (QA/QC) and economic concessions. Other unique challenges that must be accounted for are low temperatures, commonly around 4°C (50° F) at seabed, low fracture gradients, enlarged hole sizes due to high rate of penetration (ROP) drilling, and environmental regulations due to returns at seabed. The cement system must be designed for all the above aspects, and still maintain excellent integrity to enable the BOP stack to be installed upon a firm foundation. This study will describe a new simplified cement system which exhibits excellent slurry properties necessary for a deepwater environment. Laboratory results and engineering procedures will be reviewed to demonstrate that all necessary qualities for mitigation of shallow hazards are met. Furthermore, logistical and HSE advantages will be highlighted, and two case histories will be discussed.
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Dual Function Reverse Demulsifier and Demulsifier for the Improvement of Polymer Flooding Produced Water Treatment
More LessAdding partially hydrolyzed polyacrylamide (HPAM) to flood water for enhanced oil recovery has resulted in some difficulties for treatment and re-injection of produced water at Daqing Oilfield of China: Production of the injected HPAM increased water phase viscosity and emulsification of the produced fluid, leading to more oil carry-over; The state-of-art cationic water clarifiers showed poor compatibility with HPAM containing produced water due to formation of very sticky oily flocs which seriously pollutes bed filters and slop oil recovered in produced water treatment. Throughputs of existent produced water treatment facilities had to be lowered by up to 50% so that the HPAM containing produced water might be treated to re-injection specifications. As an alternative for the state-of-art cationic water clarifier, a nonionic reverse demulsifier and demulsifier consisting of both water soluble and oil soluble active components respectively for water clarification and water-in-oil emulsion breaking, was developed as a water dispersible micro-emulsion mixture. Injected into high water-cut o/w produced fluid prior to the initial oil/water separation, the dual function chemical greatly enhanced flocculation and coalescence of the oil droplets in the reverse crude oil emulsion while maintaining adequate emulsion breaking capability for downstream crude oil dehydration, leading to less oil carry-over and looser emulsion in the influent water of produced water treatment facilities. In one field application, injected at a dosage of 15mg/L into the polymer flooding produced reverse crude oil emulsion upstream of oil/water separation, the dual function chemical reduced the oil content in the influent water of a produced water treatment facility from 2004mg/L to 443mg/L, and lowered the oil content in the effluent water of bed filters from 31mg/L to 4.1mg/L without application of water clarifiers.
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