Beschreibung: Publication date: October 2017 Source: Petroleum Exploration and Development, Volume 44, Issue 5 Author(s): Li ZHANG, Zhidong BAO, Yanbo LIN, Yuming CHEN, Xiaohai LIN, Luxing DOU, Bin KONG Abstract Based on outcrop, core, logging and mud logging data, and modern deposition analog, the sandbodies genetic types and spatial distribution in different facies belts of the shallow water delta in the first Member of Cretaceous Yaojia Formation (K 2 y 1 ) of Qian'an area in Changling sag of southern Songliao Basin were analyzed, and the sedimentary model of shallow water delta was established according to deposition process. Active channel sandbodies, point bar sandbodies and bifurcation bar sandbodies in distributary channels and complex sandbodies formed the main sandbodies in the delta plain, while terminal distributary channels and mouth bar sandbodies formed the main sandbodies in the delta front. The delta prograded gradually under the construction of river mouth and reconstruction of river erosion, the early delta front evolved into delta plain and was reformed by distributary channels, and new delta fronts were formed at the river mouth ahead constantly. Under the control of the above deposition process, the size of main distributary channels in delta plain-delta front declined, while mouth bars developed increasingly. The sandbodies of different genetic types formed framework of river-dominated shallow water delta. The point bar and active channel sandbodies in main distributary channels of the delta, with the best reservoir quality, are lithologic reservoir targets in future exploration.

Beschreibung: Publication date: February 2018 Source: Petroleum Exploration and Development, Volume 45, Issue 1 Author(s): Xinhua MA, Jun XIE The Ordovician Wufeng Formation-Silurian Longmaxi Formation organic-rich shales distributed widely and stably in Southern Sichuan Basin were investigated based on drilling data. Geological evaluation of wells show that the shale reservoirs have good properties in the Yibin, Weiyuan, Zigong, Changning, Luzhou, Dazu areas, with key parameters such as TOC, porosity, gas content similar to the core shale gas production zones. Moreover, these areas are stable in structure, good in preservation conditions and highly certain in resources. The shale reservoirs have a burial depth of 4 500 m or shallow, a total area of over 2×10 4 km 2 and estimated resource of over 10×10 12 m 3 , so they are the most resource-rich and practical areas for shale gas exploitation in China. Through construction of the Changning-Weiyuan national demonstration region, the production and EUR of shale gas wells increased significantly, the cost of shale gas wells decreased remarkable, resulting in economic benefit better than expected. Moreover, the localized exploration and development technologies and methods are effective and repeatable, so it is the right time for accelerating shale gas exploitation. Based on the production decline pattern of horizontal wells at present and wells to be drilled in the near future, at the end of the 13th Five Year Plan, the production of shale gas in southern Sichuan Basin is expected to reach or exceed 10 billion cubic meters per year. The resources are sufficient for a stable production period at 30 billion cubic meters per year, which will make the South Sichuan basin become the largest production base of shale gas in China.

Beschreibung: Publication date: December 2017 Source: Petroleum Exploration and Development, Volume 44, Issue 6 Author(s): Qiang LAI, Bing XIE, Yuyu WU, Ke HUANG, Xinggang LIU, Yan JIN, Wenjun LUO, Tao LIANG The petrophysical and logging response characteristics of asphaltene carbonate reservoirs were examined based on the measurement of porosity and permeability, density, compressional and shear wave slowness, resistivity and Nuclear Magnetic Resonance transverse relaxation time ( T 2 ) of cores before and after the bitumen dissolving. The results show that (1) the asphalt can damage the pore structure of the reservoir and cause reduction of effective reservoir space and permeability; (2) with the increase of asphalt content, the compression and shear wave slowness generally decrease while the density and resistivity increase; (3) with the increase of asphalt content, the compressional wave slowness and density change less, while the shear wave slowness and resistivity change larger; and (4) the T 2 values of asphalt are generally less than 3 ms, and the higher the maturity of the asphalt, the lower the T 2 value. Based on these experiments, a method based on conventional and special logging methods was presented to evaluate asphalt content, effective porosity and water saturation in asphaltene carbonate reservoirs. The method has already been applied to 80 wells in the Longwangmiao Formation of the Anyue gas field in the Sichuan Basin to pick out zones rich in asphalt on the plane, which has effectively guided the selection of well location in the gas reservoir development.

Beschreibung: Publication date: December 2017 Source: Petroleum Exploration and Development, Volume 44, Issue 6 Author(s): Hao SU, Zhengdong LEI, Diqiu ZHANG, Junchao LI, Zeren ZHANG, Binshan JU, Zhiping LI In consideration of the limited adaptability scope, low accuracy and high demand of great cost data of existent fracture prediction methods, a new fracture predicting method was advanced by implementing geological static data and production dynamic data from the Triassic Chang 6 3 reservoirs in the Huaqing Oilfield. Five constraints, lithology, sedimentary facies, thickness, rock rupture index and fracture intensity controlling the development of fractures were sorted out based on the static geological data. The multiple linear regression method was adopted to work out the quantitative relationships between the five constraints and fracture density, and the fracture density property of the whole area was calculated. Based on production dynamic data of well history, tracer, well interference test and intake profile test, the direction and distribution of fracture horizontally and vertically were figured out by reservoir engineering analysis method. The fracture density property was verified and quantitatively corrected with numerical simulation, and a 3D discrete fracture geological model in agreement with both geological cognition and dynamic production performance was built. The numerical simulation shows that the fracture model has higher fitting consistency, high reliability and adaptability.

Beschreibung: Publication date: December 2017 Source: Petroleum Exploration and Development, Volume 44, Issue 6 Author(s): Yanlong LI, Gaowei HU, Changling LIU, Nengyou WU, Qiang CHEN, Lele LIU, Chengfeng LI To deal with sand production problems during the process of producing natural gas from hydrate-bearing sediments (HBS) using reservoir-fluid extraction method, a new gravel sizing method for sand control packing named “Hold coarse while eliminate fine particle (HC & EF method)” was developed for the clayey hydrate-bearing formations. Site X, in Shenhu area, South China Sea was taken as an example to describe detailed gravel sizing procedure. On the basis of analyzing basic particle size distribution (PSD) characteristics of HBS at Site X, the formation sand was divided into two components, which are coarse component and fine component. The gravel sizes for retaining coarse component and eliminate fine component were calculated, respectively. Finally, intersection of these two gravel sizes was taken as the proper gravel size for Site X. The research results show that the formation at Site X is clayey sand with poor sorting and uniformity, proper gravel size for upper segment packing is 143−215 μm, while that for lower segment packing is 240−360 μm. In consideration of the difficulty of layered sand control operation on offshore platform, proper gravel packing size for Site X is recommended as 215−360 μm.

Beschreibung: Publication date: October 2017 Source: Petroleum Exploration and Development, Volume 44, Issue 5 Author(s): Zhonghua LIU, Lianteng SONG, Changsheng WANG, Ting SUN, Xiaoming YANG, Xia LI Abstract For transverse isotropic fast formations, the evaluation method of the least horizontal principal stress by using logging data is an important unresolved issue. An innovative method is proposed to solve this problem by derivation of five independent stiffness coefficients ( C 11 , C 33 , C 44 , C 66 and C 13 ) in this kind of formation. Based on the functional relations between acoustic anisotropy coefficients and clay volume, and that between different stiffness coefficients, which are all approved by the assorted experiment data, an effective method is built to calculate the stiffness coefficients and the least horizontal stress of anisotropic fast formations. Successful applications in the Ordos Basin illustrate that the method is complementary to that based on the horizontal shear wave velocity which is only fit for slow formations, and is applicable to evaluating rock mechanical parameters of tight oil and gas reservoirs and selecting intervals for fracturing and testing oil.

Beschreibung: Publication date: February 2018 Source: Petroleum Exploration and Development, Volume 45, Issue 1 Author(s): Xusheng GUO, Dongfeng HU, Yuping LI, Jinbao DUAN, Chunhui JI, Hua DUAN To solve the difficulties in exploration and development in Yuanba ultra-deep gas field in Sichuan Basin, SW China, the article studies the mechanism of quality reef reservoirs development and gas accumulation and innovates techniques in ultra-deep seismic exploration, drilling, completion and testing. Through the reconstruction of dynamic depositional evolution process and regional depositional framework of homoclinal ramp-rimmed platform in Upper Permian, three theories are put forward: first, “early beach-late reef, multiple stacking, arrangement in rows and belts” is the sedimentary mode for the reservoirs in the Changxing Formation of Yuanba area; second, “dissolution in early exposure stage and dolomitization during shallow burial giving rise to the pores in matrix, overpressure caused by cracking of liquid hydrocarbon during deep burial inducing fractures” is the reservoirs development mechanisms; third, “coupling of pores and fractures” controls the development of high quality reservoirs in deep formations. From correlation of oil and source rock, it is concluded that the Wujiaping Formation and Dalong Formation of deep-water continental shelf are the major source rocks in the Permian of northern Sichuan Basin. The hydrocarbon accumulation mode in ultra-deep formations of low-deformation zones is characterized by “three-micro (micro-fault, micro-fracture interbed crack) migration, near-source enrichment, and persistent preservation”. Through seismic inversion using the pore structure parameters of pore-fracture diadactic structure model, the high production gas enrichment area in Yuanba gas field is 98.5 km 2 . Moreover, special well structure and unconventional well structure were used to deal with multiple pressure systems and sealing of complex formations. A kind of integral, high pressure resistant FF-level gas wellhead and ground safety linkage device was developed to accomplish safe and environmentally friendly gas production.

Beschreibung: Publication date: February 2018 Source: Petroleum Exploration and Development, Volume 45, Issue 1 Author(s): Wenzhi ZHAO, Suyun HU, Zecheng WANG, Shuichang ZHANG, Tongshan WANG The discovery of the giant Anyue gas field in Sichuan Basin gives petroleum explorers confidence to find oil and gas in Proterozoic to Cambrian. Based on the reconstruction of tectonic setting and the analysis of major geological events in Mesoproterozoic-Neoproterozoic, the petroleum geological conditions of Proterozoic to Cambrian are discussed in this paper from three aspects, i.e. source rocks, reservoir conditions, and the type and efficiency of play. It is found that lower organisms boomed in the interglacial epoch from Mesoproterozoic-Neoproterozoic to Eopaleozoic when the organic matters concentrated and high quality source rocks formed. Sinian-Cambrian microbial rock and grain-stone banks overlapped with multiple-period constructive digenesis may form large-scale reservoir rocks. However, because of the anoxic event and weak weathering effect in Eopaleozoic-Mesoproterozoic, the reservoirs are generally poor in quality, and only the reservoirs that suffered weathering and leaching may have the opportunity to form dissolution-reconstructed reservoirs. There are large rifts formed during Mesoproterozoic-Neoproterozoic in Huabei Craton, Yangtze Craton, and Tarim Craton in China, and definitely source rocks in the rifts, while whether there are favorite source-reservoir plays depends on circumstance. The existence of Sinian-Cambrian effective play has been proved in Upper Yangtze area. The effectiveness of source-reservoir plays in Huabei area depends on two factors: (1) the effectiveness of secondary play formed by Proterozoic source rock and Paleozoic, Mesozoic, Cenozoic reservoir rocks; (2) the matching between reservoirs formed by reconstruction from Mesoproterozoic- Neoproterozoic to Eopaleozoic and the inner hydrocarbon kitchens with late hydrocarbon generation. As for Tarim Basin, the time of Proterozoic and the original basin should be analyzed before the evaluation of the effective play. To sum up, Proterozoic to Cambrian in the three craton basins in China is a potential exploration formation, which deserves further investigation and research.

Beschreibung: Publication date: February 2018 Source: Petroleum Exploration and Development, Volume 45, Issue 1 Author(s): Yuan NENG, Haijun YANG, Xingliang DENG Based on the outcrop survey, 3D seismic data interpretation, drilling data analysis, the structural patterns and distribution of fault damage zones in carbonate strata of Tazhong Paleo-uplift were established to reveal the oil and gas enrichment law in the fault damage zones. The following findings were reached: (1) Through the filed survey, the fault damage zone system consists of fault core, damage zone with branch fault and fracture network. Affected by the active nature of the major faults, the fault damage zones differ in planar pattern and scale along the major faults. (2) 3D seismic profiles reveal that there are three types of fault damage zones in carbonate strata in Tazhong paleo-uplift, strike-slip fault damage zones, thrust fault damage zones and superimposed fault damage zones. Featuring 3 flowers and 3 root belts in vertical, the strike-slip fault damage zone can be subdivided into linear type, oblique type, feather type and horsetail type in plane. Thrust fault damage zones can be further divided into fault anticline type, anticline type and slope type. As the superimposition result of the above two kinds of fault damage zones, superimposed fault damage zones appear in three patterns, intersect type, encompassment type and penetrating type. (3) Cores from wells and geochemical data show oil and gas may migrate along the major fault and laterally. The feather type in strike-slip fault system, fault anticline type in thrust fault damage zone and intersect type in superimposed fault damage zone are possible sites for high production and efficiency wells.

Beschreibung: Publication date: February 2018 Source: Petroleum Exploration and Development, Volume 45, Issue 1 Author(s): Xiong PANG, Jianye REN, Jinyun ZHENG, Jun LIU, Peng YU, Baojun LIU The relationships between crustal stretching and thinning, basin structure and petroleum geology in Baiyun deep-water area were analyzed using large area 3D seismic, gravity, magnetic, ocean bottom seismic (OBS), deep-water exploration wells and integrated ocean drilling program (IODP). During the early syn-rifting period, deep-water area was a half-graben controlled by high angle faults influenced by the brittle extension of upper crust. In the mid syn-rifting period, this area was a broad-deep fault depression controlled by detachment faults undergone brittle-ductile deformation and differentiated extension in the crust. In the late syn-rifting period, this area experienced fault-sag transition due to saucer-shaped rheology change dominated by crustal ductile deformation. A broad-deep fault depression controlled by the large detachment faults penetrating through the crust is an important feature of deep-water basin. The study suggests that the broad-deep Baiyun sag provides great accommodation space for the development of massive deltaic-lacustrine deposition system and hydrocarbon source rocks. The differentiated lithospheric thinning also resulted in the different thermal subsidence during post-rifting period, and then controlled the development of continental shelf break and deep-water reservoir sedimentary environment. The high heat flow background caused by the strong thinning of lithosphere and the rise of mantle source resulted in particularities in the reservoir diagenesis, hydrocarbon generation process and accumulation of deep-water area in northern South China Sea.