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78th EAGE Conference and Exhibition 2016
- Conference date: May 30, 2016 - June 2, 2016
- Location: Online
- Published: 30 May 2016
101 - 120 of 1034 results
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Numerical Study of Thermohydrodynamic Processes in Inclined Wells with Variable Trajectory
Authors R.F. Sharafutdinov, R.A. Valiullin, A.S. Ramazanov, A. Sharipov and T.R. KhabirovSummaryHorizontal wells is effective method of oil and gas development. One of the important tasks is production control of horizontal wells. At this case, interpretation of logging data is a very difficult task. First problem is uneven trajectory because horizontal well typically have ascending, horizontal and descending sections, in which the phase velocity and fluid holdup is changed (in this paper consider oil and water stratified flows). Secondly, in the ascending section of horizontal well can occurs countercurrent flow. Thirdly, the heat exchange between fluid phases and the surrounding rocks take place and it influence on temperature distribution.
The paper discusses a mathematical model for the calculation of fluids holdup, velocities and temperature distribution along horizontal wells with countercurrent flow. The calculation results of fluids holdup, velocities and temperature distribution are shown in paper and analysis of countercurrent flow influence are made.
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A New Correlation for Prediction of Critical Two-phase Flow through Wellhead Chokes
Authors H.R. Nasriani, M. MoradiDowlatAbad and A. KalantariaslSummaryThe first scope of this study is to develop a new accurate empirical Gilbert type critical flow correlation based on 361 actual production tests data from Middle Eastern oil fields by means of non-linear regression analysis. The second scope is to study the impact of temperature on Gilbert type critical flow correlation for these data sets.
In order to modify the Gilbert type critical flow correlation for these data sets, correlations are tuned based on available field data points using nonlinear regression method. in this study, generalized reduced gradient (GRG) algorithm of iteration was used to find the correlation coefficients based on available field data and the convergence criteria is to minimize the value of the squared sum, SS, of the difference between the real data and the estimated one.
Based on error analysis, for the oil fields, liquid flow rate prediction is improved when new approaches (including/excluding temperature) are used. It is also concluded that the accuracy of new approach to predict production rate is not expressively improved by including the temperature in choke performance correlation for this data set compared to the case without temperature.
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Case Study of Asphaltene Flow Assurance Risk Mitigation - Emerging Numerical Model to Evaluate Inhibitor Efficiency
More LessSummaryThis work was motivated for establishing a robust asphaltene flow assurance engineering in an onshore oil field that has a high risk of asphaltene precipitation in tubing. A typical counter measure was considered to apply asphaltene inhibitor, therefore, the best candidate IB-23 was selected through the two staged asphaltene dispersant test (ADT) from total nineteen samples. The IB-23 revealed high inhibiting efficiency more than 80 % at 200 ppm concentration and maintained its efficiency more than 70 % even at 10 ppm. For further evaluating persistent of inhibiting efficiency during entire field life in which operating condition in tubing is varied, an emerging technique was developed to numerically model inhibitor. Currently, any commercial software is not available for allowing such modelling of asphaltene inhibitor due to confidentiality for inhibitor’s physical data. This study achieved to model inhibiting efficiency by treating inhibitor as pseudo-resin. It could be defined using limited physical data that was available in public accessible material safety data sheet (MSDS). Consequently, the inhibiting efficiency was expressed as size-reduction of asphaltene precipitation envelope (APE) on thermodynamic plot. Comparison between APEs and vertical lift curves could provide a comprehensive prediction of the inhibitor effect at early and late field life.
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Dual and Intelligent Completions Optimize Producing Gas Wells
By M BoussaSummaryAt Hassi R’Mel field, dual completions could significantly improve output from multi-zone gas wells, but results from intelligent completions look even better.
Dual completions were used for a long time to produce wells perforated in several zones, mostly for oil wells and rarely for gas wells. To improve production in the upper zones of Algerian gas wells, a study was conducted on producing gas wells with two and three zones in Hassi-R’Mel field. Discovered in 1956, this field is 500 km south of Algiers in the Sahara Desert and is one of the world’s largest wet gas reservoirs.
Engineers at the operator, Sonatrach, studied the choice of completion method and suggested installing dual completions for wells with several zones. This study would demonstrate the necessity of using dual completions in gas producers with several reservoirs, to improve upper-zone production and avoid cross-flow from one zone to another. Initial results made it possible to conduct a technical/economic study that showed the effects on the reservoir, well equipment and investment costs.
This article discusses the advantages and disadvantages of dual completions on gas wells, and shows the profit ratio on capital costs after these completions.
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Acid Matrix Stimulation to Reveal Formation Damage in Greater Burgan Oilfield Clastic Reservoir
Authors B.S Alshammari, N.M. Rane, D.S. Almatar and A.K. AlrabahSummaryEvaluation and classification of formation damage type and magnitude is critical exercise in oil industry. Formation damage around wellbore can be evaluated from various well testing techniques, that can provide amount of the total skin factor as an overall measurement of the formation damage. This paper focus on acid matrix stimulation in a clastic reservoir in Burgan field to remove formation damage formed around well bore by drilling and completion operations in a newly drilled well. Matrix stimulation encompasses pumping processes used to improve the connection between wellbore and reservoir to remove formation damage caused by factors such as: drilling mud, cementing operation, completion fluid and perforation. Consequently, this will dominates permeability reduction in the porous media in the invaded zone. As a result of this skin damage, oil production rate will be affected and reduced, high decline rate in production, short production life time and extra pressure drawdown will be required for production. Therefore, planning a proper acid matrix stimulation treatment is essential to increase revenue from oil well by removing and overcoming skin damage resulted from drilling fluids, enhance well productivity to increase oil production rate and meet the target rate and KPI especially for newly drilled well.
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Development of a Comprehensive Well Performance Assessment in a Giant Gas Condensate Field
Authors M. Sheydaeemehr, S. Dowlati and M. PasdarSummaryProductivity loss due to condensate blockage is the main and common problem in gas condensate reservoirs around the world. In this paper, a comprehensive framework is developed to assess the performances of the different well trajectories in a giant field. The studied field is one of the world’s largest gas condensate fields located in the Middle East and has been produced for more than ten years from four non-communicating layers in Kangan-Dalan formations.
A comprehensive comparison between the vertical well and the deviated well was performed using surface testing, production history, and reservoir simulation data.
Based on the surface well testing, IPR curves show the better performance of the deviated well. It is concluded from the simulation results that, on the one hand, development of a deviated well in the gas condensate field delays the emergence of the dew point pressure, results in longer production plateau period, and delivers more cumulative production of the gas and the condensate in the life of the well. On the other hand, the vertical well causes higher condensate saturation around the well and more severe reduction in relative permeability of gas phase and productivity index of the well below the dew point pressure.
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Parametric Study of Condensate Bank Development and Well Productivity Loss in Gas Condensate Wells
Authors A. Sheikhoushaghi, M. Ghoroori and M. RasaeiSummaryCondensate bank is formed near the wellbore after bottom-hole pressure is dropped below the dew point pressure. Based on Fevang theory (1995), the main source of productivity loss in gas condensate (GC) wells is region 1 (the closet region to the wellbore), where condensate saturation exceeded critical value. The size of region 1 increases with time. The maximum condensate saturation and development of condensate bank depends on a combination of different parameters.
In this study, a parametric analysis was carried out to investigate the development of region 1 and productivity loss in the GC wells. It was found that production rate impacts the formation time of region 1, while its development with respect to pressure depletion is identical for various production rates. Increasing fluid richness results in faster development of region 1, while the effect of critical condensate saturation is in reverse.
The degree of productivity loss is mainly a function of SCAL data rather than fluid type and production rate. The maximum condensate saturation in the vicinity of wellbore is higher than PVT test condensate dropout, and depends on SCAL data. The degree and time of productivity loss can be estimated by a simple method proposed in this study.
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Porosity Calculation of Horizontal Wells when Acoustic Slowness Is Abnormal - A Case Study in Northern Ordos Basin, China
More LessSummaryOwing to the complicated borehole environment and detection characteristics of acoustic log, acoustic slowness is always partial distortion in the horizontal wells. Besides, the logging data is sometimes insufficient due to the expensive cost and imperfect technology. Therefore the porosity calculation with insufficient and partial wrong horizontal logging data becomes one of the big challenges. Such as in the Shiguhao Area which is located in northern Ordos basin, only several logs have been measured. Through the horizontal well log interpretation and formation evaluation work, we found that the acoustic slowness was abnormal in some formations by the stratigraphic correlation. Then, several factors which lead to the high acoustic slowness are summarized in this paper. For the porosity calculation in the horizontal wells, the abnormal acoustic slowness is not recommended to be used because it can be so hardly corrected that may reduce the accuracy of the calculation since others always get the defective result by acoustic correction. Meanwhile, due to the lack of density log, we propose the use of compensated neutron log instead of abnormal acoustic log to calculate porosity. Several case studies are in great consistent with oil test results which confirm the feasibility of our method.
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Geophysical Characterization of Landslides in Serbia and Bosnia and Hercegovina – A GWB Project
Authors M. Urosevic, S. Komatina, M. Burazer, K. Suto, S. Arsenovic, D. Milosevic, S. Ziramov and F. CorenSummaryContinuous, heavy rainfall commencing in May 2014 has resulted in extensive flooding in Serbia, Bosnia and Herzegovina (BiH). Thousands of landslides developed rapidly after several days of torrential rain.
Shortly after a diverse group of geophysicists and geologists got together and set out a project to investigate these landslides. The main objective was to characterize and categorize landslides and provide results that could help devise an optimum mitigation program. Prediction of the reactivation potential of landslides was also of direct interest to the investigations. In the first phase of the project investigations included simultaneous acquisition of reflection, refraction, MASW and resistivity data along 17 profiles, distributed over six different localities. In addition, a mini 3D survey was successfully recorded along steep slope. These measurements were supported by sparse drilling, logging, coring, geotechnical analysis and the airborne laser scans.
Very good agreement was achieved between different methods, despite vastly different geometry and composition of landslides. Joint analysis of resistivity images, reflection data, and P and S-velocity fields, obtained from refraction tomography and inversion of surface waves, provide new geological insights that are important for understanding the mechanism of a landslide. This will provide valuable input for a mitigation program.
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Euler Deconvolution of the Analytic Signals of Gravity Gradient Tensor for Underground Horizontal Pipeline
More LessSummaryAt present, there are few inversion methods for horizontal pipelines. In this paper, a data interpretation approach is applied to estimate the source parameters of underground horizontal ferromagnetic pipeline. The horizontal pipeline is divided into small pieces, and every piece can be regarded as a point mass to calculate the corresponding gravity gradient tensor. By superposition principle, the gravity gradient tensor of the whole pipeline is obtained. Euler deconvolution of the analytic signal of gravity gradient tensor can be solved by analytic signal instead of gravity field derivatives. The result shows that this method can estimate the source location accurately and draw the outline of horizontal pipeline effectively. Depending on high resolution and high sensitivity of gravity gradient tensor data, analytic signal has the advantage of determining the location of anomalies bodies. Euler deconvolution of the analytic signals of gravity gradient tensor is a geophysical inversion method which can estimate the boundary position of the source automatically or semi-automatically without a priori information, and eliminate the influences of structural index and background field.
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Application of In-mine Geoelectric Methods for Detecting Tectonic Disturbances of the Coal Seam Structure
Authors A. Gyulai, T. Ormos, M. Dobroka and J. Somogyi MolnárSummaryIn-mine geoelectric methods – the geoelectric seam-sounding and geoelectric transillumination – were applied for detection of fault zones in a coal mine. To determine the model parameters of the coal seam structure seam- and drift-sounding measurement were carried out along the boundary of the coal layer (roof sounding) and that of the floor (floor sounding). From the measured apparent resistivities the model parameters of the structure were determined using a joint inversion procedure ( Dobróka et al., 1991 ).The measured data were interpreted using geoelectric tomography procedure. Good agreements were found between the location of tectonic zones predicted by the interpretation and those observed during the mining extraction.
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Near-surface Seismic Interpretation to Reduce the Loss of Water Resources
Authors O.K. Tiapkin, S.A. Onyshchenko and I. MendriiSummaryNow some economically developed regions is almost exhausted the opportunity to develop their fresh water resources. The main reserve of this resource is only the decrease (liquidation) the loss of the water of the main water consumer – agriculture. First of all it’s reconstruction of irrigation systems. The results of research of humidity inhomogeneities of the upper part of a geological section may be the spatial basis of this reconstruction. The solution to this problem with near-surface velocity mapping (the determination of average velocity of this part of a geological section for any seismic systems and energy sources – up to depth of tens of meters) is shown. The maps of this velocity characteristic are easily recalculated to the density and humidity and further may be used for the spatial prognostication of near-surface humidity inhomogeneities. The tectonic origin of some of these inhomogeneities according to the results of near-surface seismic interpretation is illustrated by the example of the steppe zone area in the southwest of Russia.
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Analysis of Selected Aromatic Hydrocarbons from Drinking Water and Natural Water Potentially Affected by Shale Gas Production
Authors A.-M. Tugulea, J. Hnatiw, C. Kubwabo, R. Charon and R. StrathernSummaryIn Canada, shale gas exploration is underway in several provinces, with most of the production currently on-going in the western provinces. Public concern is growing with regard to potential impacts on the quality and quantity of water resources, most importantly drinking water. Water impact assessment requires extensive collection of baseline data sets. Re-use of produced water for hydraulic fracturing is being encouraged and knowledge of organic impurities present is important in optimising treatment processes.
Developing analytical methods for chemical indicators of shale gas exploitation impact on water sources is key for future monitoring studies. An automated SPME-GC-MS method for the quantitation of 22 aromatic hydrocarbons (BTEX, trimethylbenzenes, naphthalene, methyl and dimethylnaphthalenes) with adequate sensitivity for drinking water impact studies is described here. Drinking water samples were quenched with 0.114 M ascorbic acid, extracted using a CombiPAL autosampler equipped with a PDMS fibre and analysed using a GC-MS/MS instrument. The method was tested on untreated and treated water samples. Method sensitivity was adequate for drinking water quality testing. All analytes were stable for 14 days in all tested samples. Analyte recovery ranged from 78% for benzene to 116 % for 1,2,3-trimethylbenzene and was independent of the characteristics of the water.
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Comparative Evaluation of Ground Water Storage Using GRACE-GPS Data in Highly Urbanized Region in Uttar Pradesh, India
Authors S Arora and P.K.R. GautamSummaryIn the present effort we have tried to evaluate the Ground Water Storage (GWS) in the highly populated and industrial region of India. With this goal we selected two districts Meerut and Lucknow of Uttar Pradesh (UP) state in India.
Meerut region is highly populated and industrial compare to Lucknow. To achieve the goal, ten years data of Gravity Recovery and Climate Experiment Satellites (GRACE), Soil Moisture Contents (SMC), Rain Fall (RF) from 2003 to 2012, bore-hole data of 42 wells from May 2005 to November 2010 and one year Global Positioning System (GPS) data of the year 2012 of International GNSS Service (IGS) station LCKI of Lucknow region have been included in the study.The Meerut region which is relatively highly urbanized shows more depletion rate -2.76±0.87 cm/yr compare to the depletion rate of -1.46±0.74 cm/yr at Lucknow. After all we found that the over extraction of the groundwater due to the continuous urbanization is the major factor, which was more responsible for the depletion of ground water resource compared to the meteorological effect. If proper measurements are not taken soon to ensure sustainable ground water usage, that day is not far away when Uttar Pradesh will face a severe shortage of ground water.
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Comparison of Microtremor and Electrical Resistivity in Detecting Sliding Surface
Authors M. Kazemnia Kakhki, W. Joao Mansur and B. BamaniSummaryReconnaissance of sliding surface has always been the challenge.
Microtremor measurement is one of the most useful methods which can be applied in landslide studies. For this, Nakamura approach have been applied for detecting the subsurface conditions on a big landslide surface in NargesChal, a village in north of Iran in Golestan province.to verify the Microtremor results, Electrical resistivity method was also applied.
Therefore based on processed data, the slide surface was detected and it is distinguished that the studied region has experienced several landslides.
Processed sections show the presence of slip zones at different depth ranges on landslide face of ground surface to 30 m. The Geotechnical logs and resistivity measurements clearly outline the importance of Microtremor measurements in landslide studies for mapping bedrock depth and shear wave velocity. The present study has utilized low cost and fast field survey procedures with high resolution imaging of electrical properties of subsurface and Microtremore. The obtained results clearly display the importance of Microtremore in landslide hazard investigations. The results were controlled by geotechnical logs and Geoelectric profiles and the extracted slide surfaces were confirmed by direct subsurface information. The geology conditions were mapped during the electrical measurements. Combinations of geological information, Microtremore and Electrical resistivity results have proved to be a powerful tool for the investigation of landslides in areas of complex geology. According to SPT tests and the mentioned methods, three sliding surface was determined, one in the depth 5m, the other one in 12m and the last in the depth 25m.
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A Link between the Pressure Dependency of Elastic and Electrical Properties of Porous Rocks
Authors T. Han, B. Gurevich, M. Pervukhina and M.B. ClennellSummaryWe present a technique to invert for the stiff and compliant porosity from velocity measurements made as a function of differential pressure on saturated sandstones. A dual porosity concept is used for dry rock compressibility and a squirt model is employed for the pressure and frequency dependent elastic properties of the rocks when saturated. The total porosity obtained from inversion shows satisfactory agreement with experimental results. The electrical cementation factor was determined using the inverted porosity in combination with measured electrical conductivity. It was found that cementation factor increased exponentially with increasing differential pressure during isostatic loading. Elastic compressibility, electrical cementation factor and electrical conductivity of the saturated rocks correlate linearly with compliant porosity, and electrical cementation factor and electrical conductivity exhibit linear correlations with elastic compressibility of the saturated rocks under loading. The results show that the dual porosity concept is sufficient to explain the pressure dependency of elastic, electrical and joint elastic-electrical properties of saturated porous sandstones.
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Application of Fine Rock Physical Modeling Techniques in High-quality Reservoir Prediction of Glutenite
More LessSummaryThe Triassic Baikouquan Group in Mahu slope area has massive accumulation characteristics, and the reservoir is sandy-conglomeratic deposits of the fan delta front facies with the low porosity and permeability, and high quality reservoirs control the oil and gas distribution. Through geophysical responses and pre-stack sensitive parameters analysis, it is considered that P-wave impedance can not distinguish the effective reservoir from tight reservoirs and pre-stack inversion is an effective way to solve this problem. Because of the lack of shear wave logging data, which makes difficulty to optimize parameters and build high-precision petrophysical model to obtain high-quality shear wave data for carrying out pre-stack inversion. Through accurate calculation of shale content, porosity, fluid saturation and other parameters, we construct a reasonable petrophysical model and effectively improve the estimation accuracy of shear-wave velocity for pre-stack inversion. And through pre-stack inversion of Vp/Vs ratio, the distribution of high quality reservoir of glutenite is effectively implemented, which provides a favorable basis for well deployment and reserve confirmation and achieves excellent effects. This study is funded by the research of “Xinjiang-Daqing” and “high-density and wide-azimuth seismic exploration supporting technology research”
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Capillary Pressure as a Source for Brie’s Fluid Mixing Law
Authors G Papageorgiou, K. Amalokwu and M. ChapmanSummaryThe need to accurately predict acoustic velocities has resulted in a widespread popularity of Brie’s
effective fluid mixing law. This empirical model together with Gassmann’s
formula are used routinely in fluid substitution problems in
petroleum geophysics and seismic monitoring of carbon capture and
storage. Most attempts to justify Brie’s
model have been focused on interpretation in terms of patchy
saturation models and attaching meaning to the Brie parameter in
terms of the patch size. In this paper, using a microstructural
description of the rock and a parameter relating to capillary
pressure, we calculate an effective fluid modulus
that is very similar to Brie’s law. The fluid mixing law we propose is
independent of frequency and has a solid theoretical foundation. This
proposed law produces analytically harmonic and
arithmetic averaging at the endpoints. Our results indicate Brie-like
behaviour may not
necessarily be related to frequency and patch-size dependent phenomena.
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Study on Anisotropy Affection Factors of Longmaxi Formation Shale
More LessSummaryThe Silurian Longmaxi Formation shale in Sichuan Basin is an important shale gas reservoir for shale gas exploration in China, but the anisotropy of Longmaxi shale is not studied sufficiently. In this case, the velocity anisotropy is examined under the reservoir pressure conditions by ultrasonic testing method. The variation patterns of wave velocity in different directions as a function of confining pressure are also presented. Mineral analysis and X-Ray scanning techniques are applied to reveal the affection factors in Longmaxi shale, the result shows the mineral layer and micro-bedding are the mainly factors of anisotropy.
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A Decoupling Approach for Differential Equivalent Equations Based on Linear Approximation
More LessSummaryBulk and shear moduli of dry rocks are two key parameters for fluid substitutions and S- wave velocity predictions. Differential equivalent medium (DEM) theory is an important method to determine the effective elastic properties of dry rocks. But the differential equations for bulk and shear moduli are coupled. Based on the approximate linear relation between dry-frame modulus ratio and porosity, this paper proposes a new method to decouple the differential equations and obtain the analytic expressions for dry rock frame modulus. The applications of experiment and logging data both show the validity of the new analytic solutions in estimating P- and S-wave velocities of clastic reservoirs.
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