Lithologic Reservoirs

Predicting a thin bed (< λ/4 in thickness, where λ is the length of waveform)from the interbedded background is a challenging work for the seismic interpreters. According to the working order from strata division through plane view to thickness prediction, a workflow was proposed by using seismic sedimentological method. Besides the high-order sequence dividing, seismic lithology analyzing (90° degree phasing)and the strata slicing proposed by Zeng Hongliu in their workflow, we emphasized the importance of the following techniques in promoting the accuracy of the thin bed plan-view prediction:(1)palaeogeomorphology recovering based on compaction correction with concern of different lithology; (2)interference suppressing of the neighboring beds; (3)browsing of strata slices linked with well-logs or drilling column; (4)non-linear strata slicing. When coming to the high-order sequence recognition, the isochronism analyzing of the seismic events and the well-seismic matching were recommended. The isochronism analyzing could help us to find the seismic reflections in accordance with the geological surfaces, and the well-seismic matching is useful for high-order sequence recognition. When concerning the thin bed thickness prediction, we firstly introduced two commonly used techniques, amplitude tunning and peak frequency, then proposed amplitude-frequency blending and genetic neural network as two new valuable techniques.

Classification,characteristics and petroleum exploration of weathering crust reservoir

MAO Zhiguo, CUI Jingwei, QI Zongjin, WANG Jinghong, SU Ling

2018, Vol.30(2): 12–22 Abstract ( 608 ) PDF (19952 KB) ( 437 )

doi: https://doi.org/10.12108/yxyqc.20180202

Weathering crust reservoir has special characteristics. Combined with the discovered weathering crust reservoir in the world, the connotation of weathering crust reservoir was defined, three-level classification was made, and its characteristics and global distribution were present. The weathering crust reservoir can be subdivided into two types:uplift weathering crust reservoir and basement weathering crust reservoir. The weathering crust reservoir is distributed to almost all of the oil-gas province in the world and geologic eras. The lithology of the weathering crust reservoir includes clastic rock, carbonate, magmatic rocks, and metamorphic rock. The type of the reservoir space is included in pores or hole, fracture and fractured pores. The weathering crust of different lithology forms different hierarchical structure and reservoir space combination, and large scale distribution. Multiperiod large and medium sized unconformities developed in superimposed basins in China. It leads to wide distribution and great exploration potential of weathering crust reservoir in China. It is main to prospect basement weathering crust in the superimposed rift basins in eastern China, and uplifting weathering crust in the superimposed craton-foreland basins in the middle and western China.

Controlling factors of hydrocarbon enrichment with the type of “below source and upper reservoir” in fault concentrated zones and nearby

FU Guang, WANG Yupeng

2018, Vol.30(2): 23–29 Abstract ( 375 ) PDF (16892 KB) ( 99 )

doi: https://doi.org/10.12108/yxyqc.20180203

In order to study the oil and gas distribution law of the type of "below source and upper reservoir" in fault concentrated zones and nearby, based on the analysis of internal structure types and its genesis of the fault concentrated zones, through the study of the relationship between the reservoir forming conditions and hydrocarbon distribution in the fault concentrated zones and nearby, the controlling factors of hydrocarbon enrichment with the type of "below source and upper reservoir" in fault concentrated zones and nearby were studied. The results show that there are mainly three controlling factors of hydrocarbon enrichment:(1)Whether the boundary fault in the fault concentrated zones is the source fracture that controls the hydrocarbon accumulation, only the boundary fault in the fault concentrated zones is the source fracture can make the underlying source rocks generate and accumulate oil and gas in the fault concentrated zones and nearby target layer. (2)Hydrocarbon enrichment degree is controlled by the type of fault concentrated zones, and hydrocarbons are enriched in the back fault concentrated zones and nearby, but relatively few in the monoclinic and synform fault concentrated zones and nearby. (3)The relationship between the boundary fault and caprock controls the hydrocarbon accumulation layer, in the caprock enclosed area, hydrocarbons accumulate under the caprock, otherwise, accumulate up and down the caprock. Therefore, the above three main factors should be taken into consideration in the oil and gas exploration of the type of "below source and upper reservoir" in fault concentrated zones and nearby.

Contact relationship and main controlling factors of braided river single channel sand body: a case of braided river from Karamay in Xinjiang, Liulin and Datong in Shanxi,Yan' an in Shaanxi

YANG Youxing, JIN Zhenkui, BAI Zhongkai, GAO Yongjin, HAN Miao, ZHANG Jinhu

2018, Vol.30(2): 30–38 Abstract ( 453 ) PDF (57260 KB) ( 525 )

doi: https://doi.org/10.12108/yxyqc.20180204

The contact type and controlling factors of single channel sand body in braided river are not clear. According to the observation and analysis of the braided river outcrop profile in the field, combined with the drilling and seismic data, the contact relationship of the braided river single channel sand body was studied synthetically. The results show that the contact relationship of braided river sand body can be divided into three types, including the complete contact type, local contact type and non-contact type. These three types of sand bodies are obviously different in sand body distribution, mudstone interlayer, reservoir properties and oil-bearing property. The sedimentary facies has obvious control effect on the contact relationship between the river sand bodies. The geologic slope of the near-grained braided river sedimentary facies is also steep, the water body energy is high, and the contact relationship of the river sand body is dominated by the complete contact type. The contact relationship between the sand bodies of the far-grained braided river sedimentary facies is dominated by local contact type. Sandy braided river sand body is mainly non-contact type. When the va/vs ratio is low, the channel sand body is dominated by the complete contact type, when the va/vs ratio is moderate, the channel sand body is dominated by the local contact type;and when the va/vs ratio is high, the channel sand body is dominated by non-contact type. The research result is helpful for guiding the deployment and improvement of oil recovery in oilfield development stage.

Shallow water delta of Upper Cretaceous Yaojia Formation in Sifangtuozi area,Songliao Basin

FAN Qi, TIAN Jijun, FAN Tailiang, FENG Shuo, GE Xu, CHENG Sainan

2018, Vol.30(2): 39–49 Abstract ( 464 ) PDF (26720 KB) ( 431 )

doi: https://doi.org/10.12108/yxyqc.20180205

Sifangtuozi area is the key project for Jilin Oilfield to submit reserves and raise efficiency recently, but there is no breakthrough of Yaojia Formation due to the poor knowledge of scientific theories. Based on the data from 147 exploration wells and 300 development wells, focused on core observation from 25 coring wells, combined with petrological characteristics, sedimentary structures, seismic sections and modern sedimentary cases, the formations, sedimentary features and exploration prospects of the shallow water delta of Upper Cretaceous Yaojia Formation in Sifangtuozi area were analyzed. The result shows that Yaojia Formation can be divided into two third-order sequences (SQY1 and SQY2+3)and six fourth-order sequences (RST). In the sedimentary period of Yaojia Formation, the paleo-topography grade is less than 3°, the paleo-depth is less than 20 m, and the dry and hot paleoclimate and opening of eastern Songliao Basin, jointly contributed to the development of shallow delta and shallow to semi-deep lacustrine sedimentary system. Specifically, the natural traits of the shallow water delta comprising features of traction current and short distanced depositional process with near-provenance, with the development of enforced hydrodynamics structures, are presenting as blanket shaped morphological characteristics and imbricated aggradations seismic facies. Integrated the delta of the Ganjiang River and the Mississippi River with the studied case, it is concluded that the large scaled bed-like sand bodies developed in depositional center, are with the characteristics of horizontal long distance propulsion and vertical extensive overlap in multistage. The above knowledge will be helpful to the exploration of subtle reservoirs in southern Songliao Basin scientifically.

Sedimentary characteristics and controlling factors of beach-bar sandbodies of the second member of Shahejie Formation in Chezhen Sag

SHI Ruikun, GAO Qiuju, HAN Xiaofeng, BA Suyu, SHI Tao, HAN Min

2018, Vol.30(2): 50–57 Abstract ( 356 ) PDF (10770 KB) ( 100 )

doi: https://doi.org/10.12108/yxyqc.20180206

A certain scale of beach-bar sandbodies were developed during the sedimentary stage of the second member of Shahejie Formation in Chezhen Sag. The understanding of the law of sedimentation and migration of beach-bar sandbodies is not yet deep enough, which restricts the process of fine exploration and development of beach-bar sandbody reservoirs. In order to further clarify the law of sedimentation and migration of beach-bar sandbodies, the sedimentary characteristics and controlling factors of the beach-bar sandbodies were studied by integrating the data of core, drilling, logging and relevant test data. The results show that the beach-bar sandbodies were dominated by debris-feldspar sandstones, the grain size probability curves mainly include patterns of "1 skip + 1 suspension" and "2 skip + 1 suspension" representing wave deposition. Several types of sedimentary structures were developed in beach-bar sandbodies, mainly including wave-ripple cross-bedding and ripple crossbedding with wave influence, horizontal bedding reflecting strong hydrodynamic force, burrow pores and bioturbation structures indicating biological effect. The beach-bar sandbodies were reconstructed in-situ, which mainly developed bar facies with obvious inverted sequence, beach facies with indistinct inverted sequence and beachbar facies with positive sequence and composite sequence vertically due to the role of wave transforming incompletely in partial area. The fault activities controlled the deposits and migrations of the beach-bar sandbodies, wave actions controlled the development of the in-situ reconstructed beach-bar sandbodies, and the supplies of material sources controled the development scales of the beach bar sandbodies. The beach-bar sandbodies were entirely distributed in overall basin with characteristics of over-lake deposition with meidium-low compositional and structural maturity during the sedimentation of the second member of Shahejie Formation in Chezhen Sag. The results can provide a reference for the further exploration and development of beach-bar sandbody reservoirs of the second member of Shahejie Formation in Chezhen Sag.

Types and controlling factors of shelf margin delta of Middle Miocene in Pearl River Mouth Basin

LI Wenjing, WANG Yingmin, HE Min, CHEN Weitao, XU Shaohua, ZHUO Haiteng

2018, Vol.30(2): 58–66 Abstract ( 391 ) PDF (14274 KB) ( 509 )

doi: https://doi.org/10.12108/yxyqc.20180207

The research of shelf margin delta has important significant for the analysis of hydrodynamic conditions and exploration of deep water hydrocarbon. The high-quality 2D and 3D seismic data and well logs were used to divide the internal sequence in seismic profile, and analyze the plane attribute distribution and well logging interpretation. Three types of shelf margin delta were identified in Middle Miocene in Zhu 2 Depression of Pearl River Mouth Basin, including fluvial-dominated, wave-dominated and mutual-influenced shelf margin delta. The fluvial-dominated shelf margin delta developed in lowstand system tract in Kaiping Sag, the wave-dominated type developed in falling-stage system in Baiyun Sag. The mutual types developed in falling-stage system in Kaiping Sag. The sequence and types of shelf margin deltas are influenced by the change of sea level and hydrodynamic conditions. While the developed location close to channel position in earlier high stand tract and further extended to the shelf margin delta. What more, the main body of shelf margin delta transfers from Baiyun Sag to Kaiping sag gradually, which was affected by the local change of source supply caused by neotectonic movement, including the activities of Dongsha uplift and Yunkai uplift. Finally, the shelf margin deltas show favorable reservoir quality, which can be good oil-gas exploration targets.

Carbonate reservoir characteristics and main controlling factors of Middle Permian Qixia Formation in NW Sichuan Basin

GUAN Xin, CHEN Shijia, SU Wang, LE Xingfu, ZHANG Haoran

2018, Vol.30(2): 67–76 Abstract ( 423 ) PDF (53496 KB) ( 507 )

doi: https://doi.org/10.12108/yxyqc.20180208

The Middle Permian Qixia Formation in NW Sichuan Basin has become the important and hot exploration field in Sichuan Basin. To clear the reservoir characteristics and main controlling factors of Qixia Formation in this area, the field outcrops and drilling core observation, rock thin section examination and reservoir physical property testing were used to analyze the characteristics of petrology, reservoir space and physical properties, three-dimensional seismic data were used to recover the ancient geomorphology, and then the main controlling factors of the reservoir were discussed. The result shows that the reservoir rocks are mainly crystalline dolomite, dolomitic leopard-spot limestone/dolomite and a small amount of grainstone. A variety of reservoir spaces are developed in Qixia Formation, and different reservoir rocks develop different reservoir space types. Intercrystalline pores, intercrystalline dissolved pores, and nonselective dissolved pores and cavities are mainly developed in the dolomite reservoir. A small amount of intragranular and intergranular dissolved pores are developed in the part of grainstone. Fractures can be developed in all types of reservoir rocks. The reservoir physical properties show the characteristics of middle-low porosity and permeability, and medium-macro-crystalline dolomite has the best reservoir property. The reservoir development is controlled by multiple factors, and the high-energy shoals in the platform-margin and intra-platform are the material foundation for the formation of reservoirs. Paleogeomorphology of sedimentary period of Qixia Formation was restored by the method of the residual thickness. The result shows that the sedimentary highland not only controls the high-energy facies belt distribution but also the main development area of the late dolomitization and dissolution, thus controlling the reservoir distribution of Qixia Formation. The Zhongba-Shuangyushi structure belt (Jiange-Jiangyou region)is in the highland of Qixia Formation paleogeomorphology, and develops platform-margin shoal facies dolomite reservoir with superior physical properties and a bigger reservoir thickness and a wider area, which shows a good exploration prospect. The important viewpoint put forward for the first time that the paleogeomorphology controls the distribution of high quality reservoir provides a good way of thinking of reservoir seismic prediction.

Nanopore structure characteristics of shale based on Ar adsorption

ZHU Hanqing, JIA Ailin, WEI Yunsheng, JIA Chengye, JIN Yiqiu, YUAN He

2018, Vol.30(2): 77–84 Abstract ( 374 ) PDF (13756 KB) ( 93 )

doi: https://doi.org/10.12108/yxyqc.20180209

The microscopic pore structure has direct effect on gas bearing property of shale. Field emission scanning electron microscope (FE-SEM)was applied to describe pore morphology and types qualitatively of Longmaxi shale samples in south Sichuan Basin. Low temperature Ar adsorption experiment was carried out to measure the specific surface area (SSA), pore volume (PV) and pore size distribution (PSD) of the shale samples, and the continuous measurement of nanopore less than 100 nm was achieved. Fractal characteristics of nanopore structure were also studied by use of Frenkel-Halsey-Hill (FHH) model, and the relationships among total organic carbon content, pore structure parameters and fractal dimensions were discussed. The result shows that organic pores, intergranular pores and intragranular pores are developed in Longmaxi shale, and organic pores are dominated. The nanopores are slit shape on the Ar adsorption isotherms, and are mainly distributed in micropores and mesopores less than 10 nm, and the micropore size is mainly 0.6-0.9 nm and 1.8-2.0 nm, while the mesopore size is mainly 4.0-5.0 nm. The fractal dimension of nanopores ranges from 2.55 to 2.64, showing strong heterogeneity. Total organic carbon content controls the development of nanopores in shales. With the increase of TOC content, the number and proportion of micropores increase, and the fractal dimension also increases. All these factors complicate the pore structure of shale samples, and enhance the gas adsorption capacity of shale reservoirs. The research results have important significance for the study of nanopore structure of Longmaxi shale reservoir in southern Sichuan Basin.

Well logging identification of Carboniferous volcanic inner buried-hill reservoirs in Ke-Bai fault zone in Junggar Basin

JIN Jun, WANG Jian, YANG Zhao, LIU Jin, JI Hancheng, JIA Haibo, ZHANG Xiaogang

2018, Vol.30(2): 85–92 Abstract ( 376 ) PDF (25993 KB) ( 354 )

doi: https://doi.org/10.12108/yxyqc.20180210

Lithology of Carboniferous volcanic inner buried-hill reservoirs in the Ke-Bai fractured zone is complicated and various, so it is hard to recognize the lithology comprehensively by conventional logging data and interpretation process. On the basis of classification and naming of the rocks, hierarchical decomposition strategy was used to solve the problem of lithology identification. The main connotation of the strategy is "component identification in first, structural division later". By establishing logging parameters of M[(Δtf-Δt)/(ρb-ρf)], N[(φNf-φN)/(ρb-ρf)]and Rt/Rxo, the crossplots of N-GR, N-M and GR-Rt/Rxo were compiled. New parameters M and N are more useful to identify lithology, Rt/Rxo is sensitive to rock texture and structure by eliminating the effect of oil and water in pores, while, GR responses the levels of radioactive substances. By using the crossplots created and the method of FMI, which is visually effective in texture and structure recognition, lithology of the Carboniferous volcanic inner buried-hill reservoirs was identified. Crossplot of N-GR is useful to distinguish sedimentary rocks and volcanic rocks;N-M crossplot is effective to recognize basic volcanic rocks and intermediate volcanic rocks;Crossplot of Rt/Rxo-GR is helpful to identify lava rocks, pyroclastic rocks and subvolcanic rocks in terms of their specific textures. The identification results were tested by petrographical identification of eighteen wells and the accuracy rate was eighty-nine percent. This study establishes a new means and technique process for lithology identification in Carboniferous volcanic inner buried-hill reservoirs of the Ke-Bai fractured zone. It is also useful for comprehensive lithology identification, volcanic rocks exploration and seismic calibration of the research area.

Mixed-grid finite-difference methods for wave equation numerical modeling in time-space domain

YANG Zhe, LIU Wei, HU Ziduo, WANG Shujiang, HAN Linghe, WANG Yanxiang

2018, Vol.30(2): 93–109 Abstract ( 338 ) PDF (29494 KB) ( 123 )

doi: https://doi.org/10.12108/yxyqc.20180211

Traditional high-order finite-difference (FD)scheme (T2 M-FD)and time-space-domain high-order finite-difference scheme (TS2 M-FD)are the most widely used higher-accuracy numerical modeling methods for seismic wave equation. T2 M-FD, with its FD coefficients calculated only based on space-domain dispersion relationship, has relatively low accuracy. TS2 M-FD, with its FD coefficients calculated based on time-space-domain dispersion relationship and plane wave theory, has relatively higher accuracy. However, T2 M-FD and TS2 M-FD have the same FD scheme only using the grid points in the general coordinate system to approximate the Laplace operator in the wave equation, having not taking full use of the grid points in the rotated coordinate system to further improve the modeling accuracy. We proposed to use the grid points in the general and rotated coordinate system together to conduct difference approximation for the Laplace operator, and constructed a new kind of mixed 2 M+N style FD schemes, M2 M+N-FD for short, and derived the approach for calculating the FD coefficients based on the time-space domain dispersion relationship and plane wave theory. And then we carried out dispersion analysis and stability analysis. Dispersion analysis shows that, comparing to T2 M-FD and TS2 M-FD, M2 M+N-FD can more effectively suppress the numerical dispersion and have higher modeling accuracy. Stability analysis shows that, M2 M + N-FD has better stability than T2 M-FD, and has almost the same stability with TS2 M-FD. In the end, we conduct numerical modeling test on homogeneous and layer model with M2 M+N-FD, and implement RTM on Marmousi model with M2 M+N-FD. The high accuracy modeling and migration results demonstrate the superiority and universal applicability of M2 M+N-FD.

Accumulation conditions and seismic identification techniques of shallow gas in the Bay of Bengal

ZUO Guoping, FAN Guozhang, LYU Fuliang, SHAO Dali

2018, Vol.30(2): 110–119 Abstract ( 343 ) PDF (75373 KB) ( 211 )

doi: https://doi.org/10.12108/yxyqc.20180212

In order to identify and predict the distribution of shallow gas effectively in the Bay of Bengal, this paper demonstrated the genesis, features, and accumulations conditions of shallow gas, such as the type of shallow gas, source rocks, reservoirs and seals. According to the 3D seismic data interpretation and analysis of seismic characteristics of shallow gas, three typical characteristics of shallow gas were drawn:(1)Bright spot characteristics. It has "double track" seismic reflection and middle-high amplitude characteristics. (2)Phase reversal characteristics. It represents obvious polarity reversal phenomenon in the shallow gas boundary. (3)Low frequency. It has low frequency phenomenon in the shallow gas interval. A set of technical methods was formed to identify shallow gas, including bright spot technology, amplitude comparison method, phase attribute, frequency attribute, pre-stack AVO, etc. It provides a technical support to identify the shallow gas quickly and efficiently, and plays an important role in the shallow gas prediction and offshore geologic hazard prevention, and achieves good results in the Bay of Bengal.

Influence of fracture on rock resistivity and its application in saturation calculation

LIU Zhiying, ZHANG Chengguang, TANG Jun, XIAO Chengwen

2018, Vol.30(2): 120–128 Abstract ( 377 ) PDF (5589 KB) ( 484 )

doi: https://doi.org/10.12108/yxyqc.20180213

The accuracy of gas saturation calculation in fractured tight sandstone reservoir depends on the reliability of rock resistivity measurement, and the measurement of rock resistivity is controlled by the conductivity, occurrence, width and density of fractures. Therefore, the study of the influence of fracture on rock resistivity measurement is the foundation for establishing a formula for calculating the gas saturation of tight sandstone reservoirs. On the basis of numerical simulation, the influences of fracture conductivity, occurrence, width and density on the measurement of rock resistivity were observed. The results of numerical simulation were checked through rock resistivity experiment, and a normalized formula of rock resistivity suitable for calculating gas saturation of fractured tight sandstone reservoir was put forward, improving the dual porosity model commonly used for saturation calculation of fractured reservoirs. Finally, the improved dual porosity model was used to calculate the gas saturation of the fractured tight sandstone reservoirs in Keshen area of Tarim Basin. The calculation results show that the results of the improved dual porosity model are consistent with the characteristics of high gas saturation in rock fracture in Keshen area, and more consistent with the oil testing conclusion.

Distribution and quality heterogeneity of conglomerate reservoir: a case from upper Karamay Formation in eastern block Wu 2, Karamay Oilfield

CAO Qian, WANG Zhizhang, WANG Ye, ZHANG Dongliang, GONG Yanjie, ZOU Kaizhen, FAN Tailiang

2018, Vol.30(2): 129–138 Abstract ( 379 ) PDF (2298 KB) ( 388 )

doi: https://doi.org/10.12108/yxyqc.20180214

The upper Karamay Formation in eastern block Wu 2, Karamay Oilfield, is sandy conglomerate reservoir of fan delta, which is characterized by complex sand body distribution, strong heterogeneity and poor effect of water injection and oil production. The data of core, laboratory analysis and well logging were used to study the heterogeneity of reservoir distribution and quality. The data of practical production and the results of qualitative analysis, fine quantitative characterization and synthesis evaluation obtained by entropy method, were adopted to analyze the effects of the distribution and quality heterogeneity on the performance of actual development measure. The result shows that the inter-layer heterogeneity is generally medium. The permeability of layer is dominated by positive rhythm, compound positive rhythm and homogeneous rhythm, and the reservoir quality heterogeneity is strong. In the same sand-body controlled by facies constraints, the reservoir quality heterogeneity is medium to strong. Vertically, the S5 and S1 sand layers are consist of medium-thick sand bodies and can be divided into many layers, with other layers showing isolated single sand body form. The sand body distribution on the plane is controlled by sedimentary microfacies. The heterogeneity of reservoir distribution leads to inefficiency of injection and production. The heterogeneity of reservoir quality leads to poor effect of injection production. This conclusion is of great significance for adjusting the injection production well pattern and measures.

Efficiency improvement of CO₂ flooding in middle and later stage for low permeability reservoirs

MA Li, OUYANG Chuanxiang, TAN Zhengyang, WANG Changquan, SONG Yan, LIN Fei

2018, Vol.30(2): 139–145 Abstract ( 400 ) PDF (1352 KB) ( 740 )

doi: https://doi.org/10.12108/yxyqc.20180215

In order to solve the problems of low opening rate caused by directional gas channeling in the middle and later stages of CO2 flooding development in low permeability reservoirs, poor overall development results and potential safety issues, numerical simulation and laboratory experiments were used to analyze the effects of anti-controlled gas channeling, to ensure the production rate of oil wells and other technical methods. The results show that the CO2 of water-gas alternating is more uniform and the oil recovery efficiency is better than that of gas injection, wheel injection and continuous gas injection. When the monthly CO2 injection-production ratio is 1.7 to 1.8, it can simultaneously maintain the mixing capacity and prevent gas channeling, so as to decrease water cut and increase oil production. In view of gas channeling characteristics of oil well, different flow pressure control standards were formulated to maximize the CO2 flooding effect. The pressure field changes can be adjusted by periodic oil recovery, which can increase the frequency of oil and gas contact to promote mixed phase and expand the volume of CO2. The periodic oil recovery effect of typeⅠgas wells is better than that of type Ⅲ gas wells and the continuous oil recovery. The safety production is effectively guaranteed by adjusting the injection production ratio and controlling the reasonable production pressure difference, installing the wellhead control valve and setting up wellhead single well tank regular pressure relief. The results can provide technical reference for the development of CO2 flooding test and promotion in Jilin Oilfield and the same kind of oil reservoirs in China.

Normal annular pressure regularity in “A” annulus for high sulphur gas wells in Yuanba gas field

LUO Wei, LIN Yongmao, DONG Haifeng, XIONG Xindong, ZHANG Zhicheng

2018, Vol.30(2): 146–153 Abstract ( 339 ) PDF (1284 KB) ( 545 )

doi: https://doi.org/10.12108/yxyqc.20180216

For high Sulphur gas wells in Yuanba gas field that have a substantial increase in production, the annular pressure caused by thermal expansion effects is a kind of wellbore safety threats which cannot be ignored. Combined with the actual production situation, a wellbore temperature-pressure calculation model of gas-liquid twophase considering nonhydrocarbon correction and a prediction model of annular pressure caused by thermal expansion effects were firstly established. The normal annular pressure regularity was obtained through the example calculation and the sensitivity analysis of influencing parameters. Meanwhile, corresponding annular pressure control measures were put forward. The judgment chart of annular pressure types in the "A" annulus was established through a large number of simulation calculation with different gas production rate and water production rate. Then, the judgment chart was applied to the field, which realizes the annular pressure type judgment of three key wells in Yuanba gas field. The results show that to reduce the thermal expansion coefficient of annular fluid, to improve the isothermal compression coefficient of annular fluid and to improve the deformation coefficient of casing, are all the effective methods to control the annular pressure caused by thermal expansion effects. To reserve a part of the annular space at the beginning of production is also beneficial to reduce the annular pressure caused by thermal expansion effects.

Dynamic simulation analysis of wellbore liquid loading in gas well for Linxing gas field

CHEN Huan, LI Zihan, CAO Yanfeng, YU Jifei, LI Menglong

2018, Vol.30(2): 154–160 Abstract ( 357 ) PDF (4125 KB) ( 438 )

doi: https://doi.org/10.12108/yxyqc.20180217

The number of liquid loading well in Linxing gas field is increasing gradually, and the lack of measured water production rate and bottom hole pressure makes it difficult to predict the wellbore liquid loading, which seriously affects the normal production and economic benefit of gas well. In order to reveal the process of the wellbore liquid loading in gas well, combined with the characteristics of gas well production tubing and the testing data of wellbore pressure, a set of dynamic prediction method of wellbore liquid loading in gas well suitable for Linxing gas field was established. The result shows that the dynamic prediction method can be used to simulate the dynamic process of wellbore liquid loading in gas well and quantitatively calculate the volume of wellbore liquid loading, so as to accurately calculate the height of wellbore liquid loading in gas well. The method can solve the problem for predicting wellbore liquid loading in gas well, and has a certain guidance and reference significance for the development of Linxing gas field.