Table of Content

10 February 2019, Volume 41 Issue 1

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Mechanism of Complex Modes of the Pore Structure of Sandstone/Conglomerate Reservoirs

YIN Senlin, CHEN Gongyang, CHEN Yukun, WU Xiaojun

2019, 41(1):  1-17.  DOI: 10.11885/j.issn.1674-5086.2018.01.01.01

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The formation mechanism of complex modes of the pore structure of sandstone/conglomerate reservoirs is still unclear. Thus, this study investigated the difference mechanisms of lithofacies classification, pore structure modes, and displacement efficiencies based on experimental data of 325 core examples through mercury intrusion porosimetry, cast thin sections, scanning electron microscopy, and X-ray computed tomography. The results reveal that, taking both oil field exploitation and utility into consideration, lithofacies of sandstone/conglomerate reservoirs can be classified to 3 primary categories, 7 secondary categories, and 13 tertiary categories. They have different pore structure modal characteristics and relatively great variance in their efficiency of displacement by water injection. Single-mode rock particles are mostly coarse sandstones with highly developed and relatively well inter-connected pores in a network structure. The displacement by water injection is mainly via connected networks, resulting in higher efficiency. Dual-mode rock particles are composed of two classes of particles:conglomerates and medium-coarse sandstones. They have relatively developed and moderately inter-connected pores in a sparse network structure. The displacement, here, is mainly via star-shaped connected networks, with ordinary efficiency. Complexmode rock particles consist of three types of particles:conglomerates, medium-coarse sandstones, and silt or mud. Their pores are moderately developed and relatively poorly inter-connected with a star-shaped networking structure. The water injectiondriven displacement is mostly scattered over local high-permeability zones, resulting in poor overall efficiency. The same lithofacies typically show different pore structure modes while different lithofacies can have identical structure modes. Differential transformation due to particle configuration and diagenesis leads to different pore structure modes for identical lithofacies; while sorting, rounding, and arrangement of particles result in identical pore structure modes for different lithofacies.

Quantitative Characterization of Heterogeneity and Geological Modeling of the Yingmai X1 Dolomite Oil Reservoir

CAO Peng, DAI Chuanrui, ZHANG Chao, CHANG Shaoying, LIU Jiangli

2019, 41(1):  18-32.  DOI: 10.11885/j.issn.1674-5086.2017.11.08.01

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The Yingmai X1 dolomite oil reservoir has entered the ultra-high water-cut exploitation stage; therefore, it is particularly important to quantitatively characterize the heterogeneity of the reservoir and determine the distribution pattern of residual oil. This study examines the field geologic outcrop, and the results are integrated with characteristics of individual boreholes. We find that the heterogeneity of the Yingmai X1 dolomite oil reservoir is primarily controlled by sedimentation cycles and lithological properties. High-quality reservoirs are mostly located in fine to medium-grained dolomite. Low-permeability bands formed by micritic dolomite influence fluid seepage behavior. The six low-permeability stratigraphic frameworks developed in the reservoir predominantly govern the distribution pattern of the residual oil. By calculating the true thicknesses of stratigraphic layers and using thin-layer inversion techniques, stratigraphic frameworks were constructed and applied as constraints in establishing geological and numerical models for oil reservoirs. It is estimated that the residual oil reserve in the dolomite region amounts to 133.33×10⁴ t and production can reach 22.9×10⁴ t if appropriate measures are introduced. The methodology of this study can be a valuable reference for exploiting similar oil reservoirs.

The Reservoir Characteristics and the Pore Evolution of Yingshan Formation in Gucheng Region, Tarim Basin

ZHANG Shaonan, HUANG Baiwen, SUI Huan, YE Ning, LI Yingtao

2019, 41(1):  33-46.  DOI: 10.11885/j.issn.1674-5086.2018.08.31.01

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This study focuses on the pore evolution during the diagenetic period of the Yingshan Formation in the Gucheng region in the Tarim Basin. Specifically, the petrophysical characteristics, diagenetic effect, and reservoir characteristics of the target layers are investigated based on the analysis of core description, flake identification, cathodoluminescence, well logging data, and geochemical data. The results show that reservoir rocks of Yingshan Formation in Gucheng region are primarily composed of limestone and dolomite. Of which, the dolomite is mostly distributed in the lower section of the Yingshan Formation. Furthermore, the fine grained automorphic-semi-automorphic dolomite and medium-coarse crystalline dolomite both exhibit relatively good porosity. The reservoir space is mainly made up of intercrystalline pores, intercrystalline pores and cracks, which forms three types of reservoirs including the crack type, pore type, and crack-hole type reservoirs. The diagenetic effect has a significant impact on the storing performance of the reservoir in the research region. In particular, the early cementation, compaction and pressure dissolution, silicidation, and filling of hydrothermal minerals have a destructive effect on the primary pores. The dolomitization, rupture, and hydrothermal dissolution in the shallow burial are constructive diagenetic effects. Affected by the transitional dolomitization, the intercrystalline pores in dolomites exhibit a low degree of development. The hydrothermal dissolution effect plays a key role in the formation of high-quality reservoir.

Characteristics and Controlling Factors of High-quality Dolomite Reservoirs in the Permian Qixia Formation, Northwestern Sichuan

BAI Xiaoliang, YANG Yueming, YANG Yu, WEN Long, LUO Bing

2019, 41(1):  47-56.  DOI: 10.11885/j.issn.1674-5086.2017.12.25.02

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The characteristics and primary controlling factors of high-quality dolomite reservoirs in the Qixia Formation in the northwestern Sichuan Basin were studied based on the diversity of their genesis and distribution. Through field studies, observation and analysis of cores and lamellae, and interpretation of well log images, the lithology and spatial characteristics of the Qixia Formation reservoir were summarized and the patterns of distribution of dolomite reservoirs in the Qixia Formation were analyzed. Finally, the main factors controlling the development of high-quality dolomite reservoirs in the Qixia Formation are discussed. It is believed that (1) the particle size in the Qixia Formation-coarse-grained dolomite and sugary dolomite-reflect a significant increase in the thickness of grain-bearing facies in the uplift near the end of the Carboniferous fully demonstrates that the paleogeomorphology before the Permian deposition controlled the distribution of beach facies in the Qixia Formation. (2) The Qixia Formation in the northwestern Sichuan Basin is a phased dolomite reservoir. The primary reservoir lithology is subhedral-euhedral-coarse grain dolomite, saccharoid-subhedral-intermediate grain dolomite, with obvious residual particle imaging, intergranular development of porosity, replacement of bright-grain limestone with dolomite, and inheritance and adjustment of intergranular pores in the original limestone. (3) The Qixia Formation in northwestern Sichuan experienced multiple hydrothermal activities in deep-buried conditions, and development of intergranular dissolution pores in medium-to-coarse-grained dolomite and dissolution pores in the dolomite crystal face. Beach-phase dolomite superimposed with buried hydrothermal activity and tectonic fracture reconstruction have resulted in large-scale distribution of high-quality dolomite reservoirs.

Investigation of the Typical Oil Reserves and Selection of Exploration Fields of the Dabasong Fan, Eastern Slope of the Mahu Depression

QIAN Haitao, BAI Yu, YOU Xincai, LI Peng, YIN Lu

2019, 41(1):  57-67.  DOI: 10.11885/j.issn.1674-5086.2017.11.07.06

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The eastern slope of the Mahu Depression in the Junggar Basin possesses excellent conditions for oil reserve formation and characteristics indicative of an oil reserve of large area. The region has been scarcely explored, so it is a key area for oil and gas exploration. To determine the oil reserve formation pattern along the eastern slope of the Mahu Depression and to allow in-depth oil and gas exploration in the region, data from boreholes, cores, seismology, and analytical tests were integrated and techniques such as palaeo-geomorphology reconstruction, sedimentary facies characterization, and reservoir prediction for gravel-containing medium to coarse sandstones were employed. The oil reserve characteristics, main controlling factors, and exploration fields of the Triassic Baikouquan Formation at the DA13 site in the north wing of the Dabasong Fan were examined. The results demonstrate that the oil reserve is a fault-lithologic reservoir and is mainly jointly controlled by faults and largescale wide and gentle platform zones, slope breaks, and favorable front facies belts. While oil accumulation and sand bodies are determined by tectonics and slope breaks, respectively, the reserve itself is controlled by both lithology and faults. Therefore, by comparing the reserve formation conditions, it is confirmed that the south and north wings of the Dabasong Fan have similar reserve formation backgrounds and conditions. By analyzing the single-well facies and the seismic facies, large-scale favorable front facies belts and multiple fault-lithological traps are noted under the south wing of the Dabasong Fan. The region has great potential for exploration and is the favorable site for expanding oil and gas exploration in the Baikouquan Formation along the eastern slope of the Mahu Depression.

Patterns and Comprehensive Predictions of Fracture Development in Bedrock Gas Reservoirs in Dongping, Qaidam Basin

LI Xiang, LIU Yingru, CHAI Xiaoying, LONG Wei, BAI Yadong

2019, 41(1):  68-76.  DOI: 10.11885/j.issn.1674-5086.2017.11.15.01

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Located in the front eastern section of the Altyn-Tagh in the northwestern Qaidam Basin, the Dongping bedrock reservoir is the largest complete bedrock buried hill gas reservoir recently discovered in the terrestrial basins of China. Nevertheless, due to natural fractures in gneiss and granite bedrocks and karst caves in the region and their complex formations, the area is highly heterogeneous with significant yield differences between wells. In addition, mass exploitation of a large-scale gas reservoir is relatively difficult. Because fractures are the key factor in allowing high and stable yields of bedrock reservoirs, it is especially important to conduct research on patterns and comprehensive predictions of fracture development in the reservoir of interest. Hence, lithological and physical properties and reserve types of the reservoir were examined, followed by statistical analyses based on core samples, thin sections, and well imaging. We found that the fracture system of the Dongping bedrock reservoir is dominated by tectonic fractures, accompanied by two types of dissolution fractures. The statistics of individual wells were used as standards to divide the study area according to its lithology. The Post-Stack Amplitude Direction Decomposition (PADD) technique was employed to predict the horizontal distribution of fractures in the study area. Finally, the results were integrated and analyzed with yield data. According to the relative relationships between different lithological zones, different fracture types, yields, and transformation effects, the study area was divided into three effective fracture development zones. One is a natural high-yield zone, while the other two are potential areas requiring appropriate transformation measures. Comprehensive predictions of reservoir potential in the study area were performed, and the predicted results matched actual yields at a rate higher than 70%.

Reservoir Architecture-based Classification of Seepage Barriers of Flow Unit

WAN Qionghua, LUO Wei, LIANG Jie, CHEN Chen, YANG Qiufei

2019, 41(1):  77-84.  DOI: 10.11885/j.issn.1674-5086.2018.05.08.01

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With more in-depth investigations on various reservoir architectures, the theories of reservoir architectures have become increasingly mature, but application of the research results remains lagging. In this study, based on existing research on the architecture of typical braided stream reservoirs, a braided stream reservoir in the A Oilfield is divided into various architectural elements, such as the braided channels, mid-channel bars, silt layers, and troughs on bars. Criteria and methods for recognizing the seepage barriers and the connected bodies of braided stream reservoirs are analyzed and summarized, in order to provide intuitive guidance for oil and gas field exploration. The results reveal that the recognition of seepage barriers and the connected bodies establishes a linkage between the static architectural model at the pre-exploration stage and the dynamic classification of flow units at the exploration stage of oil reservoirs. Different classes of seepage barriers constrain different types of flow units. The development of seepage barriers directly impacts the types of the surrounding flow units and, thereby, affects the fluid movement pattern in the oil reservoir.

P-wave to S-wave Velocity Ratio Scanning Method Based on the Sinc Interpolation and Correlation Spectrum

WANG Jian, WU Bo, XU Tianji

2019, 41(1):  85-90.  DOI: 10.11885/j.issn.1674-5086.2018.01.11.01

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In the multi-component seismic technique, accurate extraction of the P-wave to S-wave velocity ratio (γ) is an important step in multi-component data processing, inversion, and interpretation. As the wave impedance ratio for the same underground layer is the same, the reflected P-wave and reflected converted wave are interrelated at this layer. The P-wave to S-wave velocity ratio and time ratio can be mutually converted. In the P-wave to S-wave velocity ratio scanning method based on the sinc interpolation algorithm and correlation coefficient spectrum analysis, a series is set, and the sinc interpolation algorithm is used to cross-correlate the stretched P-wave with the converted wave. When the cross-correlation coefficient reaches its maximum value, the corresponding ratio can be obtained. The effectiveness, accuracy, and practicality of this method are verified through testing with both theoretical and actual data.

Study on Stress Sensitivity of the Formation Factors of Low-permeability Sandstones

LIU Zhongqun, CHEN Meng, LI Min

2019, 41(1):  91-101.  DOI: 10.11885/j.issn.1674-5086.2017.09.12.02

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To explore the influences of effective stress variations on the formation factors of the low-permeability sandstone reservoirs in the Ordos Basin, the formation factors of seven core samples under varying confining pressures (p_c) and internal pressures (also known as pore pressures, p_p) were obtained experimentally. Experimental data were analyzed based on Biot's definition of effective stress and response surface functions. It is found that the effective stress coefficient (α) obtained through the response surface secant method can characterize the effective stress more accurately. Also, α is discovered not to be a constant at 1.00, but be distributed within the range of 0.04～0.60, having certain functional relationships with the confining and internal pressures. It is confirmed that the formation factors of low-permeability sandstone reservoirs change non-linearly with the effective stress and that microfractures are the main cause of non-linear variations in effective stress. An equivalent microfracture model was established based on the microscopic structure of the cores. It was integrated with the theory of rock resistivity to deduce the functional relationships between formation factor and effective stress and to characterize the variation pattern of formation factors of low-permeability sandstone reservoirs under the action of non-linear effective stresses.

Experimental Study on Hot Water Flooding in Tight Sandstone Reservoir to Reduce Water Injection Pressure and Increase Injection Capacity

YANG Shukun, GUO Hongfeng, ZHAO Guangyuan, JI Gongming, ZHANG Bo

2019, 41(1):  102-110.  DOI: 10.11885/j.issn.1674-5086.2018.04.04.02

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To investigate the use of hot water flooding to reduce water injection pressure and increase injection capacity in tight sandstone reservoirs, laboratory-based physical models were used to study the effects of hot water flooding on clay minerals from the target block in terms of hydration-induced expansion, rock pore structure, oil-water viscosity, crude oil thermal expansion, oil-water interfacial tension, oil and water phase starting pressures, and oil-water relative permeability curve. The mechanisms by which hot water flooding reduced water injection pressure and increased injection capacity in tight sandstone reservoirs were analyzed, and the effectiveness of hot water flooding at achieving these processes was assessed for a range of hot-water temperatures. Our experimental results showed that hot water flooding was highly effective at reducing water injection pressure and increasing injection capacity. Increase in the temperature of the water flood decreased the starting pressure of water injection and weakened the impact of the peak effect, thus improving the ability of the water flood at reducing water injection pressure and increasing injection capacity. The effectiveness of hot water flooding differed with the permeabilities of the rock cores and generally improved with decreases in the permeability coefficients of the rock cores. Finally, it was found that the optimal temperature for hot water flooding in the targeted tight sandstone reservoir block was approximately 100℃.

Study of the Transport Mechanism of Low-speed Displacement in Eccentric Annulus of Horizontal Wells

SUN Jinfei, LI Zaoyuan, LUO Pingya, ZHANG Ganggang, JIAO Shaoqing

2019, 41(1):  111-118.  DOI: 10.11885/j.issn.1674-5086.2018.01.11.03

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When displacing the cementing of horizontal wells, it is usually difficult to realize the replacement in turbulent flow because of instrumental limitation. In laminar flow, however, the transport mechanism of two-phase flow in the eccentric annulus can be quite complex. Based on the computational fluid dynamics method, we developed a geometric and numerical model, tracked the displacement interface of two-phase flow using the fluid volume method, and analyzed the transport mechanism of displacing fluids in the eccentric annulus of horizontal wells under various displacing flow rates. The following conclusions are drawn from the results:(1) With a low eccentricity, one-time use of isolation fluid can realize 90% displacing efficiency. When the eccentricity is greater than 0.5, the displacing efficiency becomes relatively small. In this case, increasing the amount of isolation fluids cannot further increase the displacing efficiency; (2) Considering the severe eccentricity of the casing, reducing the flow rate from 1.0 m/s to 0.2 m/s can help stabilize the interface and results in 6.8%higher displacement of drilling oil. Furthermore, this approach can also resolve the retention issue on the narrow side and pointing issue on the wide side; (3) The cementing displacement process in the eccentric annulus of horizontal wells is affected by multiple factors, including the eccentric effect, gravity effect, and viscous effect. These factors interact and inhibit with each other. Therefore, a reasonable design of cementing process parameters based on the actual well conditions on site can not only improve cementing quality, but also reduce cost and increase efficiency.

Prediction of Dynamic Sanding in Unconsolidated Sandstone Reservoirs of Bohai Oilfield

LI Jin, XU Jie, GONG Ning, HAN Yaotu, GAO Bin

2019, 41(1):  119-128.  DOI: 10.11885/j.issn.1674-5086.2018.04.08.01

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The accurate prediction of the risk of sanding is a key technological measure for sanding prevention. The Bohai Oilfield currently utilizes static methods for sanding prediction, which do not account for changes in ground stress, water saturation, reservoir pressure depletion, and pressure drawdown during oil production processes, and these have dynamic effects on reservoir sanding. This results in significant difference between the sanding predictions of the methods used and reality, and these predictions only provide general guidance for sanding prevention design. In this work, we investigated commonly used well completion methods in the Bohai Oilfield, namely oriented perforating and horizontal open hole wells, and constructed a method for predicting dynamic sanding throughout the lifecycle of an unconsolidated sandstone reservoir in the Bohai Oilfield based on analyses of the factors and mechanisms governing dynamic sanding and mechanical stabilities of wellbores. Our method provides a comprehensive analysis of the dynamic effects of ground stress, water content, pressure drawdown, and pressure depletion on reservoir sanding, thus enabling dynamic predictions and analyses of sanding risks throughout the petroleum extraction lifecycle of a reservoir. In practice, it was shown that our proposed method predicted the sanding of unconsolidated sandstone reservoirs in a more precise, accurate, and realistic manner than existing methods. The findings of this study will therefore contribute to optimization of sanding prevention measures, thus reducing costs and improving productivity.

Optimization of Parameters for Well Flushing via Hot Fluid Circulation in Offshore Electric Submersible Pump Wells Clogged by Wax Deposits

YANG Wanyou, ZHENG Chunfeng, LI Ang, WANG Lei

2019, 41(1):  129-136.  DOI: 10.11885/j.issn.1674-5086.2018.04.18.02

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To investigate the distribution patterns of wellbore temperature fields during well flushing via hot fluid circulation in electric submersible pump (ESP) wells of the Bohai Oilfield, we constructed a computational model for the temperature fields of wellbores during hot fluid circulation in ESP wells based on the principle of conservation of heat. This model accounts for effects associated with the heating of the ESP, electric cable cooling, volume of hot fluid injection, injection depth, injection temperature, heat transfer in the wax-clogged pipeline segments, and thermal conductivities of seawater and air. Using this model, we analyzed the effects of injection temperature and injection volume on the wellbore temperature distribution of mixed production fluids. The results of this study show that the temperature distributions of mixed production fluids along the wellbore are positively correlated with increases in injection temperature and injection volume. Our model can be used as a guide to dewaxing processes in the field, thus prolonging the dewaxing cycles in wax-prone wells and reducing the rates at which fluid and oil production decrease over time.

A 3-D Physical Simulation Experiment and Numerical Test on Multi-thermal Fluids Flooding After Huff and Puff

LIU Dong, SU Yanchun, CHEN Jianbo, ZHANG Caiqi, PAN Guangming

2019, 41(1):  137-146.  DOI: 10.11885/j.issn.1674-5086.2017.11.07.02

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Aiming at the problems of injection multi-thermal fluids (the mixture of the high temperature of steam, hot water, nitrogen and carbon dioxide), such as more components, more complex mechanism, different from conventional steam injection etc., a 3-D physical simulation experiment and numerical test on multi-thermal fluids flooding after huff and puff is carried out. Based on similarity criterion and taking a typical block of heavy oil in bohai oilfield as the prototype, a scaled three-dimensional physical model is established firstly. And the corresponding law between multi-thermal fluids flooding production performance and the stage of heated chamber extending is researched by three-dimensional physical simulation experiment of multi-thermal fluids flooding after huff and puff by horizontal wells. Then, the numerical simulation software stars module was used to establish the numerical model, on the basis of history matching of physical model, three numerical tests of multi-thermal fluids flooding, steam flooding and steam compound nitrogen to carbon dioxide flooding are carried out, and the temperature field and production performance are contrast analyzed. Finally, the best injection production parameters of N heavy Oilfield are optimized by numerical tests. The results can provide guidance and reference for the multi-thermal fluids flooding plan design of heavy oilfield.

Development and Application of Gas Injection for Oil Recovery from Offshore Oilfields

FENG Gaocheng, HU Yunpeng, YAO Weiying, ZHANG Yu, YUAN Zhe

2019, 41(1):  147-155.  DOI: 10.11885/j.issn.1674-5086.2018.07.18.01

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The proportion of offshore low-permeability reservoirs and heavy oil reservoirs in untouched geological reserves has shown an annual increase. Thus, identifying methods for effective use of such hard-to-access reserves has become a major issue. Although gas injection for oil recovery has been applied both domestically and internationally for decades, China's offshore gas injection technology is still in its beginning stages. Focusing on these problems, this study examines the theory and application of gas injection development in both China and the world. Considering the current state of development and the production difficulties of China's offshore oilfields, seven constraints of the development of offshore gas injection technology in China were first analyzed, and solutions and measures were then proposed. The research shows that the potential use of gas injection for oil recovery technology in offshore oilfield applications is great and that localizing key technologies and applying multiple methods can reduce developmental risks and increase economic benefits.

Analysis of Drainage Process for Crude Oil Production Using Pipeline with Large Drop-in-height

LIU Enbin, MA Xi, LI Chun, XIANG Min, HUANG Liyu

2019, 41(1):  156-164.  DOI: 10.11885/j.issn.1674-5086.2018.04.18.01

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For oil-after-water commissioning that involves a maximum drop-in-height of 1 432.64 m and uses a crude oil pipeline containing a U-shaped section with a large drop-in-height, the density difference between crude oil and water leads to stagnation issues in the oil head. To resolve this problem, we proposed to drain the pipeline and release pressure using a pressure relief valve installed in the valve chamber near the oil-water interfacial point. Based on the OLGA multiphase flow transient simulation method and taking the actual situation as an example, we simulated the gas-driven water drainage process in the pipe section with a large drop-in-height. Specifically, the simulation focused on analyzing the change in flow rate and pressure over time with varying diameters of the leakage aperture. A series of available sizes of the leakage apertures and corresponding changes in the displacement, flow, and pressure over time were obtained from the simulation. The results demonstrate that the maximum displacement in the selected pipe section (capacity≈6 367.98 m³) can reach 3 375 m³. From the perspectives of economy, safety and effectiveness, the best leakage aperture range was found to be 90～110 mm. This number was consistent with that in the actual situation. This study provides a practical basis for alleviating similar abnormal conditions in real production processes.

Improved Genetic Algorithm and its Application in the Design of Drilling Fluid

LI Jian, CAI Haiyan, LI Jiadi

2019, 41(1):  165-174.  DOI: 10.11885/j.issn.1674-5086.2018.04.26.03

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The selection of a proper drilling fluid system is the key to enabling fast and high-quality drilling operations while avoiding or reducing the occurrence of drilling accidents when working in deep wells, ultra-deep wells, and complex formations. When designing the drilling fluid using case-based reasoning (CBR), the drilling fluid system can be derived from multiple attributes such as lithology, well type, and well depth. However, the derivation results can be substantially affected by each attribute's weight assignment. The genetic algorithm suffers from slow convergence and low convergence precision when used for optimization of the attribute weights. Considering this issue, this study proposes an improved genetic algorithm to address the issue of attribute weight assignment in CBR. Initially, the genetic operator is improved using the following techniques. An exponential scale transformation method is used to optimize the selection of the individual operator. A self-adaptive adjustment is performed on the scale factors in the arithmetic crossover. With reference to the mutation operator, the mutation direction of each individual is modified to maintain the diversity of the population. Next, the self-adaptive adjustment of the crossover probability is realized from two aspects, namely the individual fitness and the level of variation between crossover individuals. Finally, by performing comparative experiments on the UCI dataset, we proved that the improved genetic algorithm can enhance the global convergence performance and increase the accuracy of CBR. Experimental results demonstrate that applying the improved genetic algorithm to the CBR-based drilling fluid design can effectively optimize the weight assignments of each attribute and therefore improve the quality of drilling fluid.

Simulation of Deep Filtration Process for Wastewater Containing Polymers and Optimization of Technical Boundaries

WANG Zhihua, LI Jiexun, ZHOU Nan, BAI Ye, XU Yunfei

2019, 41(1):  175-186.  DOI: 10.11885/j.issn.1674-5086.2018.06.30.01

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This study addresses the problem of unbalanced water injection and production in a ground system. Based on the existence of insufficient wastewater sources following deep filtration treatments and lack of precious clean water sources in oilfields, this study considers the technology of a two-stage deep filtration treatment that utilizes "double-layered filter material+ three-level graded filter material" after ordinary treatment of polymer-containing wastewater. The advanced treatment technology of two-stage filtration considers variations in polymer concentration and its correlation with filtration process parameters. A numerical simulation is conducted to describe the aggregated distribution characteristics of oil beads and suspended particles in the flow field of the deep filtration process. This is necessary to determine changes in the content of oil and suspended solids in filtered water following deep filtration. The results show that it is feasible to control the water quality indices of oil and the content of suspended solids to within 5.00 mg/L by performing deep filtration on the polymer-containing wastewater. An optimized technical boundary relationship map of the deep filtration technology for polymer-containing wastewater can be used to enhance the indicators and efficiency of its treatment. The operational load and stability of the polymer-containing wastewater treatment process can also be ensured.