Lithologic Reservoirs

Marine sediment developed widely in China, and ancient carbonate rock is the main exploration field for large-scale reservoir. Large-scale reservoir reserves were found in the Sinian and Cambrian in Sichuan Basin, in the Cambrian and Ordovician in Tarim Basin and in the Ordovician in Ordos Basin. The ancient carbonate rock is characterized by abundant oil and gas resources, great hydrocarbon generation potential of argillaceous source rocks and various reservoir types in palaeohigh. Oil and gas exploration in the future should be concentrated in the multiple oil and gas accumulation belt in large-scale paleohigh, formation dissolution belt controlled by regional unconformity, reef flat in platform margin and particle beach symbiotic with evaporate. Marine black shale sediment widely developed in Sichuan Basin is an important field for shale gas exploration, and there are great prospects of unconventional oil and gas exploration.

Fine characterization of accreting body of mouth bar in Ⅰ-11 sublayer at lower member of Lower Gancaigou Formation in Yuejin Ⅱ Oilfield

MOU Zhonghai， LIAO Chun， DING Xiaojun， CHEN Yuan， YU Yue

2014, Vol.26(6): 8–14 Abstract ( 444 ) PDF (2178 KB) ( 588 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.002

This paper analyzed the mouth bar in the E31 Ⅰ-11 sublayer in YuejinⅡ Oilfield of Qaidam Basin by using well logging, geological data and application configuration analysis. The research suggests that there developed two mouth bars, two kinds of configuration units and five accreting bodies in the E31 Ⅰ-11 sublayer. Mouth bar is limited by restraining barrier as the identification of fifth interface,between accreting bodies is mudstone interlayer as the identification of fourth interface. According to the research of the configuration units combination in space, splicing between two mouth bars, mouth bar and sheet bar splicing, and mouth bar lateral accretions exist in the direction vertical to the source, and mouth bar progradation and retrogradation exist in the direction parallel to the source. There are aggradation-positive cycle and aggradation-reverse cycle between configuration units on the vertical. Reverse rhyme is the main characteristic in configuration unit, followed by positive rhythm. On the basis of the above research, the plane distribution map of five accreting bodies was completed.

Abnormal high pressure and its relation to hydrocarbon accumulation in Raoyang Sag

WANG Zhihong， LI Jianming

2014, Vol.26(6): 15–19 Abstract ( 489 ) PDF (1183 KB) ( 295 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.003

Abnormal high pressure is widely distributed in Shahejie Formation of Raoyang Sag, which is closely related with hydrocarbon accumulation. Based on the logging data, this paper analyzed the distribution and forming mechanism of abnormal high pressure by equilibrium depth method.The results show that abnormal high pressure is mainly distributed in hydrocarbon generation sag areas, and it decreases towards the margin of sag.Uncompaction caused by rapid deposition and the hydrocarbon generation are the main reasons for the forming of abnormal high pressure. The effects of abnormal high pressure on hydrocarbon accumulation are significant. On one hand,abnormal high pressure is an important dynamic source for hydrocarbon migration. On the other hand, abnormal high pressure controls the distribution of oil and gas under certain geologic conditions. The reservoirs are always found in high pressure formations or surrounding high pressure areas. Meanwhile the fluid potential resulted from abnormal high pressure drove fluids to migrate from the center to the margin of sag, and oil and gas are distributed around hydrocarbon generation sag.

Geological conditions for shale oil forming of Middle Jurassic Dameigou Formation in the northern margin of Qaidam Basin

FU Xiaodong， RAO Dan， QIN Jianzhong， SHEN Baojian， XU Jin， YANG Zhenheng

2014, Vol.26(6): 20–27 Abstract ( 574 ) PDF (2027 KB) ( 383 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.004

Based on field geologic section investigation, core observation, geologic test and drilling data, this paper analyzed the development characteristics, organic geochemical behavior, rock mineral features, reservoir properties and oil bearing capability of shale of the seventh member of Dameigou Formation in the northern margin of Qaidam Basin. The result shows that the shale with rich organic matter of J2d7 is thick vertically and continuous laterally, with high organic abundance and good organic type to generate oil. The lithologic assemblage types of J2d7 shale are various, the percentage of brittle minerals is high, and it developed many kinds of pores and has high content of occluded oil. Comprehensive study demonstrates that shale of Jhas basic geological conditions to form shale oil, and it is the best favorable target for shale oil exploration. Yuka fault depression, Hongshan fault depression, Ounan sag and Delingha fault depression may be the favorable areas for shale oil exploration.

Research on differences of lateral sealing between transoid fault and cisoid fault

FU Guang， LANG Yue， HU Xinlei

2014, Vol.26(6): 28–33 Abstract ( 466 ) PDF (1636 KB) ( 367 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.005

In order to study the controlling of faults to oil-gas accumulation and distribution in oil-gas-bearing basin ， based on the study of lateral sealing mechanism of fault and its influencing factors ， the differences of lateral sealing between transoid fault and cisoid fault were studied by analyzing the sealing characteristics between transoid and cisoid fault. The result shows that the differences of lateral sealing between transoid fault and cisoid fault are mainly showed in the following three aspects: ①the place of fault zone connected transoid fault and cisoid fault with reservoir is different ， the sliding crush zone of transoid fault connects with reservoir ， while the induced fracture zone of cisoid fault connects with reservoir; ②the lateral sealing objects of transoid and cisoid fault is different ， the lateral sealing object of transoid fault is mudstone of the other block ， while lateral sealing object of cisoid fault is fault-rock; ③the lateral oil-gas sealing capacity of transoid fault is different from that of cisoid fault, and theoretical and actual example research all show that the lateral oil-gas sealing capacity of transoid fault is stronger than that of cisoid fault

Provenance analysis of heavy minerals of the second member of Sanjianfang Formation in Shanshan arcuate belt, Tuha Basin

ZHANG Jingqi， HAN Xiaofeng， YANG Zhanlong

2014, Vol.26(6): 34–39 Abstract ( 573 ) PDF (1827 KB) ( 328 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.006

Based on the analyses of correlation, factor, Q type cluster, stability coefficient, plane assemblage features and paleogeomorphology, this paper studied the heavy mineral components of the second member of Sanjianfang Formation in Shanshan arcuate belt. The result shows that the source rock types are mainly sedimentary rock and metamorphic rock, which respectively responds to the primary provenance in Takequan uplift in the north and the secondary provenance in Liaodun uplift in the southeast. The provenance in Takequan uplift controls the sedimentation of braided delta fan in hill country, and the provenance in Liaodun uplift controls the sedimentation of braided delta fan in Wenjisang area. The eastern hill country is the intersection of Takequan uplift provenance and Liaodun uplift provenance.

Sedimentary characteristics and genesis of thick layer sand body of Chang 8₂ sublayer in Ordos Basin

YAO Jingli， CHU Meijuan， BAI Chang’er， YUAN Xiaoming， GUO Zhengquan

2014, Vol.26(6): 40–45 Abstract ( 604 ) PDF (2541 KB) ( 438 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.007

Based on core observation, combining with data analysis of well log and laboratory test, this paper analyzed the sedimentary characteristics of Chang 8 2 sublayer, and restored the sedimentary environment and sedimentary evolution. The result shows that Chang 8 2 sublayer belongs to regressive system tract, and experienced a complete MSC （ from lake ingress to lake retreat ） . In the early-middle period, lake district expanded with relatively deeper water, and the sedimentary environment is mainly delta front subfacies, with mouth bar developed. In late period, it is plain and swamping deposition, and mainly developed distributary channel microfacies, the thickness of the sand body is thin, and physical properties are poor. Rapid accumulation of the mouth bar controlled by lake shoreline is the main cause of the growth of Chang 8 2 thick sand body.

Heterogeneity of shale reservoirs based on CT images

XU Zuxin

2014, Vol.26(6): 46–49 Abstract ( 666 ) PDF (969 KB) ( 1068 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.008

In order to study the heterogeneity of shale mineral components, this paper analyzed the CT scanning images of shale by using digital image processing techniques, studied the distribution characteristics of shale mineral components, and discussed the relationship between the content of mineral components and fractal dimension. The research results show that the density of shale mineral components on the CT image is much greater than that of organic matter and micro pore structure, so the mineral components are easy to identify. At the same time, the distribution of shale mineral components have fractal characteristics, showing a certain self-similarity, and the fractal dimension of mineral components can reflect the heterogeneity of mineral components. The study on shale heterogeneity based on CT images is an effective supplement of shale reservoir evaluation, and it can guide the evaluation of shale brittleness.

Characteristics of inner buried hill clastic reservoirs and their main controlling factors in Kongnan area, Huanghua Depression

ZHANG Jing， LI Shuangwen， FU Lixin， LONG Liwen， YAO Jun， LU Yi

2014, Vol.26(6): 50–56 Abstract ( 648 ) PDF (2260 KB) ( 295 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.009

The Upper Paleozoic clastic buried hill is an important field for oil and gas exploration in Kongnan area of Huanghua Depression, and the lower Shihezi Formation is the main gas formation with low degree of exploration. The study on the reservoir characteristics and controlling factors of lower Shihezi Formation is still a blank field. Based on the analysis of ordinary thin sections, cast thin section, scanning electronic microscope and physical properties, this paper studied reservoir characteristics of the lower Shihezi Formation in Kongnan area and their influencing factors. The result shows that clastic rock reservoir of the lower Shihezi Formation belongs to braided river sedimentary system, rock types are mainly gray medium-coarse graind lithic quartz sandstone and feldspathic sandstone of channel microfacies, the reservoir space of inner buried hill mainly includes secondary intergranular dissolved pores and structural fracture, the porosity and permeability are 5%～10% and 0.5～10 mD respectively, and the reservoir is a cracked-poroustype with super-low porosity and extra low permeability. Deposition, diagenesis and tectonization are the three factors controlling the reservoir quality, of which microfacies, lithofacies and tectonization determine the formation and development of buried hill inner reservoir, and favorable reservoirs are laterally distributed in the stacked area of channel and diara sand and fracture-developed zones. This comprehensive study shows that the reservoir of type Ⅰ is located in the principal part of the thrust structure zone and the main reservoirs to increase production in the future.

Study on sedimentary facies of the third member of Shahejie Formation in Lin 7 fault block, Huimin Sag

LUO Wei， HE Youbin， MA Bo

2014, Vol.26(6): 57–63 Abstract ( 556 ) PDF (2468 KB) ( 373 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.010

Based on core observation, combining with data of regional geology, analysis assay and well logging, this paper systematically studied the sedimentary facies of the third member of Shahejie Formation （ Es 3 ） in Lin 7 fault block of Huimin Sag. It is considered that the study area developed delta, turbidite fan and lacustrine facies. The delta can be further divided into microfacies of underwater distributary channel, interdistributay bay, mouth bar, distal bar and prodelta mud, the turbidite fan can be further divided into microfacies of channel, interchannel, lateral frontchannel, margin channel and outer fan mud, and the lacustrine facies mainly developed semi-deep to deep lake mud. In the plan, the sediment in Es 3 spreaded along WN-ES direction. In vertical profile, the delta deposite mainly developed in lower Es 3 , the turbidite fan and the semi-deep to deep lacustrine mainly developed in middle and upper Es 3 . From lower Es3 to upper Es 3 , sand body experienced progradation to retrogradation repeatedly, and moved from west to east gradually, and the water is deepening gradually on the whole, including some short decreasing. This study of sedimentary microfacies provides geological basis for the comprehensive reservoir research of Es 3 in Lin 7 fault block.

Characteristics of lower assemblage reservoir of Yanchang Formation in Dingbian-Ansai area ， Ordos Basin

WANG Bianyang， HE Yonghong， WANG Kangle， WANG Yanlong， DONG Lihong， LI Airong

2014, Vol.26(6): 64–68 Abstract ( 627 ) PDF (2113 KB) ( 574 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.011

Based on the data of thin sections, casting thin sections, scanning electron microscope and core analysis, this paper studied the petrology characteristics, physical properties and influencing factors of lower assemblage reservoir of Yanchang Formation in Dingbian-Ansai area. The result shows that Wuqi and Ansai area are mainly feldspathic sandstone because the sediment source is single, and the sandstone rock types in Dingbian and Zhidan area diversified by different source rocks and are mainly arkose and lithic arkose. The reservoir space of lower assemblage reservoir of Yanchang Formation mainly includes primary intergranular pores and secondary dissolved pores. The reservoir is characterized by low-ultra-low porosity and low-ultra-low permeability. The reservoir properties are affected by sedimentary microfacies and diagenesis. The reservoir properties in Wuqi and Dingbian area are best, the next is in Zhidan area, and the reservoir properties in Ansai area are poor. In longitudinal, the reservoir properties of Chang 10 are the best, the next is Chang 9, and the reservoir properties of Chang 8 and Chang 7 are poor.

Quantification of late Paleogene uplift in Nanyang Sag using acoustic velocity

WANG Zhongnan， LIU Guangdi， CHEN Wan， YANG Yuran， GUO Feifei， TANG Hui

2014, Vol.26(6): 69–74 Abstract ( 522 ) PDF (1785 KB) ( 583 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.012

The abnormal pressure is not common in Liaozhuang Formation and the first member of Hetaoyuan Formation in Nanyang Sag, and acoustic velocity is mainly controlled by maximal historical burial depth. Typical wells that located in the center and the margin of the sag were selected to investigate the relationship between acoustic velocity and depth of mudstone of Liaozhuang Formation and the first member of Hetaoyuan Formation, and then the uplift of the late Paleogene was qualified based on velocity-depth trend and velocity data. The result shows that the uplift ranges from 400 m to 1 000 m, the uplift in the western and southern part is relatively low and it increased gradually toward the northeast to about 1 000 m. Based on the analysis of horizontal distribution of uplift, it is considered that the large scale uplift near Weigang-Beimazhuang structural belt caused the occurrence of subnormal pressure. Decompression, increasing in volume and petroleum pumping function during uplift increase reservoirs space, forming lower potential area, thus contributes to oil and gas accumulation.

Pathway system and its controlling on hydrocarbon accumulation in Weibei Sag

LIN Yuxiang， WANG Yuwei， MENG Cai， HAN Jilei

2014, Vol.26(6): 75–82 Abstract ( 516 ) PDF (2114 KB) ( 474 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.013

As the passageway of hydrocarbon migration, the pathway system is very important for hydrocarbon accumulation. In terms of the research of fault and its activity, depositional system and unconformity in Weibei Sag,we put forward that there are three kinds of pathway system factors including sand body, fault and unconformity surface. They formed fault-unconformity pathway system and fault-unconformity-sand body pathway system. Weibei Sag has two hydrocarbon source areas which are located at the northern depression belt and eastern Zaohu faultednose belt. The eastern Zaohu faulted-nose belt developed lots of complex fracture structure, but the northern depression belt developed little faults. Weibei Sag developed six unconformity surfaces,among which Ng/Es4 or Ng/ Ek1 and lower Ek2/Ek3 are regional unconformity surfaces. For these reasons, different regions developed different pathway system in Weibei Sag. Based on the analysis of reservoirs in Weibei Sag and the characteristics of pathway system, we concluded the controlling of different passage system on hydrocarbon migration and accumulation. We find that sand body pathway system may control the forming of lithologic pinchout reservoirs and sand lens reservoirs, fault pathway system may control the forming of unconformity-fault reservoirs, fault-block reservoirs and structurallithologic reservoirs, fault-unconformitypathway system may control the forming of fault-block reservoirs, lithologic reservoirs and fault-lithologic reservoirs, and fault-unconformity-sand body pathway system may control the forming of lithologic pinchout reservoirs, unconformity reservoirs, fault-block reservoirs and fault-lithologic reservoirs. The study result is favorable for reservoir exploration and prediction in Weibei Sag.

Reservoir characteristics and controlling factors of the Triassic Baikouquan Formation in Mahu slope area, Junggar Basin

TAN Kaijun， WANG Guodong，LUO Huifen，QU Yongqiang，YIN Lu，CHEN Juan

2014, Vol.26(6): 83–88 Abstract ( 681 ) PDF (1824 KB) ( 306 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.014

By means of rock slices, casting slices and scanning electron microscope, this paper systematically studied the petrologic feature, reservoir space type, pore throat structure, physical properties and controlling factors of the Triassic Baikouquan Formation in Mahu slope area, Junggar Basin, to find out the effective reservoirs in this area. The study results show that: ①The reservoir type is mainly glutenite of fan delta plain and front subfacies, which is characterized by low compositional and structural maturity, poor to moderate pore throat structure, plain subfacies is dominated by primary pores, and front subfacies is mainly of secondary pores, with low porosity and permeability on the whole. ②The area developing rigid particles has the characteristics of weak compaction, high corrosion mineral content, strong dissolution and preferable physical properties. ③The plain subfacies has higher compaction degree, higher matrix content, weaker dissolution and poorer physical properties, comparing to the front subfacies. ④The compaction can reduce the pores obviously, the cementation can not, the dissolution can increase pores, and the hydrocarbon emplacement has definite inhibitory effect on diagenesis, which is helpful to improve the reservoir properties

Thermolytic dynamics and hydrocarbon generation characteristics of Maoming Oil Shale: Taking the geological model of Qiongdongnan Basin as an example

LIU Chang， SU Long， GUAN Baowen， ZHENG Youwei， CHANG Jiang， ZHENG Jianjing

2014, Vol.26(6): 89–97 Abstract ( 549 ) PDF (2606 KB) ( 541 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.015

In view of the natural gas generation and prediction problems under the condition of offshore high geothermal field, taking the geological model of Qiongdongnan Basin as an example, natural gas generation process was simulated by heating immature Maoming Oil Shale samples with kerogens of Ⅱ type and coal samples from the Qiongdongnan Basin with kerogens of Ⅲ type. In order to determine the characteristics of the yields of oil and gas generation derived from pyrolysis, we adopted the hydrous pyrolysis experiments in the closed system and non-isothermal anhydrous pyrolysis experiments in the open system. The dynamics quantitative models of hydrocarbon generation of various hydrocarbon compositions in different evolution stages show that the range of activation energy distribution derived from different components of coal is much wider than that of Maoming Oil Shale. Among them, the ranges of activation energy distribution for methane, ethane, propane and heavy hydrocarbon（C4～6） generated by Maoming Oil Shale derived from pyrolysis are from 38 to 86 kcal/mol, 44 to 92 kcal/mol, 43 to 77 kcal/mol and 46 to 70 kcal/mol respectively. And the dominant frequency of activation energy are 52 kcal/mol, 54 kcal/mol, 63 kcal/mol and 48 kcal/mol respectively, their percent are 20.44%, 38.04%, 42.5% and 25.05% respectively,and the pre-exponential factors are 6.47×1011 s-1, 2.70×1012 s-1, 1.09×1015 s-1 and 8.39×1015 s-1 respectively.Using the kinetic methods of natural gas generation, combined with the thermal history data from Qiongdongnan Basin, we contrasted the prediction of natural gas generation between Maoming Oil Shale and coal. It indicates that coal of type Ⅲ releases hydrogen more slowly than Maoming Oil Shale of type Ⅱ during the thermal evolution, suggesting a lower hydrocarbon generative rate but a longer thermal evolutionary phase of hydrocarbon generation. The results reveal that: similar to the hydrocarbon source rocks of coal-measures in Yacheng Formation of Qiongdongnan Basin, Maoming Oil Shale in high thermal evolutionary phase still has fine potential of natural gas generation under the condition of offshore high geothermal field. This study is more theoretical and practical significance to coal-type gas exploration and development in the wider areas of Chinese Sea.

Study on major secondary minerals in volcanic reservoir in Xujiaweizi area, Songliao Basin

LI Xin， DU Dedao， CAI Yuwen， WANG Shan

2014, Vol.26(6): 98–105 Abstract ( 508 ) PDF (1831 KB) ( 361 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.016

Based on the volcanic rock core observation of more than 50 wells in Xushen Gas Field,this paper studied the deep volcanic reservoir in Xujiaweizi area in northern Songliao Basin. The result shows that the rock types of deep volcanic reservoir include basic rock, neutral rock and acidic rock, with the acidic rock being dominated. Volcanic lava includes basalt, andesite, trachyte and rhyolite, while volcaniclastic rock includes tuffs, rhyolitic ignimbrites, volcanic breccia and agglomerate. Through thin section observation by microscope, it is discovered that the volcanic rocks are in a variety of different degrees of metasomatism which formed many secondary minerals such as laumontite, chlorite, quartz,feldspar, siderite, calcite and clay mineral filling in pores and cracks. The characteristics of these secondary minerals were detailedly described and their forming thermodynamics conditions were simulated according to the third law of thermodynamics. According to the chemical equation of laumontite, chlorite and quartz, combined with the ionic concentration of K+, Ca+, Na+，H+, （Fe, Mg）2+ and （Fe, Al）3+ in formation water, we can work out the equilibrium constant K, and then calculate the ΔG（P，T） values under different temperature and pressure according to the equation ΔG（0T）＝ -R·T·ln K. By comparing the ΔG（P，T） values of laumontite, chlorite and quartz, the formation time order was determined. The chlorite is formed firstly then the quartz, and the last one is laumontite. The thermodynamic simulation result can be proofed by microscope observation, which provides thermodynamics proof for the study on diagenetic evolution of secondary minerals in volcanic reservoir.

Using J-function method to calculate saturation of carbonate reservoirs

SIMA Liqiang， LI Qing， YANG Yi， CHEN Qiang

2014, Vol.26(6): 106–110 Abstract ( 604 ) PDF (1355 KB) ( 602 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.017

Calculating the initial water saturation of heterogeneous carbonate reservoirs is always a challenge to log interpretation, especially under the condition of lack of data such as sealed core which can directly determine the water saturation. Taking an oilfield in the Middle East as an example, according to the data of capillary pressure curve, physical properties analysis and RFT test, this paper discussed J-function method that uses capillary pressure curve to calculate initial water saturation of heterogeneous carbonate reservoirs. The water saturation calculated by this method agrees quite well with that interpreted by relative permeability experiment data and oil test results. This study provides a reasonable and reliable method to ensure water saturation of heterogeneous carbonate with no water saturation of cores.

Application of matching pursuit wavelet decomposition and reconstruction technique to reservoir prediction and gas detection

CHEN Sheng， OUYANG Yongling， ZENG Qingcai， BAO Shihai， LI Xingyu， YANG Qing

2014, Vol.26(6): 111–114 Abstract ( 549 ) PDF (1800 KB) ( 724 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.018

The weathering crust karst reservoir in central Sichuan area is characterized by complex fracture-cavity system, strong heterogeneity and abnormal seismic reflection, which causes unobvious seismic response and AVO, and increases difficulties in reservoir perdition and gas detection. On the basis of matching pursuit algorithm, used wavelet decomposition and reconstruction technique to effectively eliminate the effect of mudstone, and then carried out reservoir prediction and gas detection, achieving good results. Wavelet decomposition and reconstruction technique can be used to decompose seismic data into wavelet with different shapes, frequency and energy, and then reconstruct wavelet reasonably, with higher resolution in both time domain and frequency domain. This study provides a new idea and method for complex reservoir prediction with strong reflection and gas detection.

Law of pressure drop along the horizontal wellbore in heavy oil reservoir

YUAN Lin， LI Xiaoping， ZHANG Jiqiang， CHENG Ziyang

2014, Vol.26(6): 115–119 Abstract ( 539 ) PDF (904 KB) ( 519 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.019

Horizontal well technology had been widely used in developing heavy oil reservoir. But for the high viscosity of heavy oil, the pressure drop along the horizontal wellbore had been a problem that can not be ignored in studying the productivity of horizontal well. Based on the productivity analysis theory of conventional horizontal well, this paper used the method put forward by Joshi to divide the three-dimensional seepage field into two two-dimension seepage fields, applied the conformal mapping method and law of equivalent percolation resistance to get the flow model in porous media of horizontal well in heavy reservoir, and considering the variable mass flow along the horizontal wellbore, built the coupling model between reservoir and wellbore. Case study shows that the pressure drop along the horizontal wellbore makes the absolute open flow decreased by 7.7%, moreover the value of pressure drop in the horizontal wellbore in heavy reservoir is far greater than that in conventional reservoirs. Sensibility analysis indicates that as the increasing of horizontal well length, power law index and reservoir thickness, the pressure drop along the wellbore also increases, while as the increasing of wellbore radius, the pressure drop decreases. This study can offer a new idea to research the law of pressure drop in the horizontal wellbore in heavy reservoir.

Influence of non-Darcy flow on deliverability of gas-water producing horizontal well in low permeability gas reservoirs

ZHANG Jiqiang， LI Xiaoping， YUAN Lin， WANG Wenbin， WANG Chaowen

2014, Vol.26(6): 120–125 Abstract ( 501 ) PDF (1260 KB) ( 323 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.020

When water drive gas reservoir is exploited to a certain extent, the water will be produced, and then gas and water two-phase flow will increase the resistance of gas flow, which leads a sharp decline on gas well production. The determination of reasonable gas well deliverability is the foundation of scientific development of gas field and has very important guiding significance. According to the change of gas and water two-phase seepage rule, based on stable percolation theory, this paper introduced pseudopressure and threshold pressure gradient of gas and water two-phase, and established a new gas well productivity prediction model for gas-water producing horizontal wells, taking the influences of threshold pressure gradient, slippage effect, stress sensitivity, formation damage and high-speed nonDarcy into account. Studies show that the water/gas ratio has a rather greater impact on the deliverability of gas well, so water breakthrough must be controlled during the gas production. With the increasing of threshold pressure gradient, stress sensitivity and water/gas ratio, the deliverability of gas well decreases, while with the decreasing of slippage effect, the deliverability of gas well increases. The gas phase threshold pressure gradient plays a more important influence on the gas deliverability than water phase threshold pressure gradient.

Recoverable reserve growth of discovered gas fields

ZHANG Jingping， TANG Hongjun， SUN Yuping

2014, Vol.26(6): 126–130 Abstract ( 402 ) PDF (873 KB) ( 379 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.06.021

The application of improved recovery techniques and extension of old reservoirs can improve recoverable reserves in discovered gas field. By calculating the annual growth factor or cumulative growth coefficient of previous recoverable reserves and establishing recoverable reserves growth model, we can predict the future recoverable reserve growth. Currently, the U.S. recoverable reserve growth model is extensively used in America and other regions. This paper used this model to match historical data of recoverable reserves of 186 gas fields in China. The result shows that the actual recoverable reserves are in agreement with the recoverable reserves predicted by this model, which indicates that the model has certain applicability in China. Finally, this paper used the model to estimate the future recoverable reserves of the fields discovered before 2011 in China.