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Zhao X.,Southwest Petroleum University | Zhao X.,Sichuan Key Laboratory of Natural Gas Geology | Zhao X.,China University of Petroleum - Beijing | Wu S.,China University of Petroleum - Beijing | And 2 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2012

Deepwater turbidity channel reservoirs are usually located in deep sea areas, where a distant spacing pattern for development wells is often allocated due to the cost constraint of prospecting operation. Consequently, the characterization of such underground reservoir architectures of deepwater turbidity channels with the current overlay method for multi-well models used mainly under dense-well pattern conditions usually achieves a poor precision. Therefore, based on drilling and seismic data of a distant well spacing pattern for deepwater turbidity channel reservoirs of the Akpo oilfield in Niger Delta Basin, West Africa, we introduced a novel method to characterize such turbidity channel reservoir architectures in terms of well-to-seismic integration, and discussed its conception and procedures as well. Reservoir architectures of deepwater turbidity channels can be classified into three orders, channel system, channel complex and single channel. Of which the channel complex can be further subdivided into two suborders, channel complex series and channel complex. Various orders of architecture units differ significantly from each other in scale, thus, a well-to-seismic integration of individual oil measures, sublayers and internal sections within sublayers guided by architecture models should be applied to adapting an architecture model of different orders to downhole data (including dynamic data) and seismic information as well as to fulfilling the characterization of reservoir architectures of deepwater turbidity channels. This study will not only have a significantly economic value in efficiently developing deepwater turbidity channel reservoirs but also be of guiding significance for integrating well data with seismic data to characterize architecture elements. Source


Yan J.-P.,Sichuan Key Laboratory of Natural Gas Geology | Yan J.-P.,Southwest Petroleum University | Wen D.-N.,Southwest Petroleum University | Li Z.-Z.,Sinopec | And 3 more authors.
Natural Gas Geoscience | Year: 2015

Low permeability is a salient feature of Es3 reservoirs in the southern slope of Dongying Sag. And the complex pore structure makes it difficult to unify electrical parameters, which brings some difficulties to evaluating reservoir saturation. The pore structures of low permeability sandstone reservoir in Es3 are analyzed, based on core physical properties, casting thin sections and mercury injection data. It is divided into 3 categories and 5 subcategories, combined with rock electricity experiment data to extract rock-electrical parameters “a” and “m” from different pore structure of reservoir in Es3. Along with the wellbore profile, using well logging response characteristics, a comprehensive method is established. It can identify different pore structure types and determine the rock-electrical parameters of different pore structure types. As a basis for further saturation calculation, it effectively improved the accuracy of low permeability sandstone reservoir saturation interpretation. © 2015, Science Press. All right reserved. Source


Yan J.-P.,Sichuan Key Laboratory of Natural Gas Geology | Yan J.-P.,Southwest Petroleum University | Wen D.-N.,Southwest Petroleum University | Li Z.-Z.,Southwest Petroleum University | And 4 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2016

The low permeability sandstone reservoir, which has been an important target of exploration and development for oil and gas increase in reserves and production, is difficult to identify accurately because of the complex pore structure. The pore structure classification of complex low permeability sandstone and the investigation of the petrol-physical diversity of rock samples in different types are helpful to determine the reservoir type and the fluid properties of low permeability sandstone reservoir. After the analysis of the pore structure based on physical properties data, mercury injection, nuclear magnetic resonance data and the considering of the properties division level standard of clastic reservoir (SY/T 6285-2011), the low permeability sandstone of Es4 in the southern slope of the Dongying sag is divided into three types of pore structures. And the diversity of every type in mercury injection, nuclear magnetic resonance (saturated T2 spectrum, centrifuged T2 spectrum and free-fluid T2 spectrum), the pore throat distribution, the porosity and permeability are discussed. Many results indicate that the T2 spectrum and capillary pressure curves could reflect the pore throat distribution in some degree. Meanwhile the T2 spectrum could be used to evaluate the pseudo capillary pressure curve to get the pore throat radius. However, it's large of the deviation between the pore throat distribution from this way and mercury injection because of the membrane bound-water affect. In fact, the free-fluid T2 spectrum and the pore throat distribution of mercury injection correspond much better. Based on this feature, after the comparing of the free-fluid T2 spectrum and the pore throat distribution of mercury injection in different pore structure types, the conversion relationship is established between the relaxation time and the pore throat distribution of mercury injection in different pore structure types and the pore size scale (large scale-linear relationship; small scale-piecewise exponential function). Meanwhile, the electrical standards and identification methods of every pore structure are also established based on the cross-plot analysis of logging response. Therefore, the pore structure could be identified along the well hole, and then the pore throat distribution of different pore structure can be quantitatively calculated by using nuclear magnetic resonance logging data. Not only the segment of pseudo-capillary curve's building is avoided, but also the identification of pore structure could be more effective. Overall, this research provides a direct evidence to recognize the low permeability reservoir and sheds a new light on quantitative reconstruction of microscopic pore structure with well logging. © 2016, Science Press. All right reserved. Source


Chen S.,Southwest Petroleum University | Chen S.,Sichuan Key Laboratory of Natural Gas Geology | Zhang H.,Southwest Petroleum University | Lu J.,Southwest Petroleum University | And 11 more authors.
Petroleum Exploration and Development | Year: 2015

Based on observation of cores and casting thin sections, reservoir fluorescence, hydrocarbon geochemical characteristics and oil production test data, the factors controlling the tight oil accumulation and high production in the Da'anzhai Member in the Jurassic Ziliujing Formation in central Sichuan Basin are studied. The shelly limestone, muddy shell limestone and tight limestone are all oil-bearing in the Da'anzhai Member. The dissolved pores and fractures in shelly limestone and the matrix pores (microfractures, intercrystal pores) in tight limestone are all oil-bearing in large area, which is the reason why oil wells can keep low production for a long period of time. On the basis of the extensive oil-bearing, natural gas from the Upper Triassic Xujiahe Formation provided the major power for oil migration and accumulation in the Da'anzhai low amplitude, water-free tight limestone reservoirs, driving the dispersed oil from the matrix pores into an accumulation, so the oil is more enriched in the western structures of central Sichuan Basin where oil wells are higher in gas-oil ratio. In contrast, in the east of central Sichuan, the Huayingshan major faults generally cut through Da'anzhai Member, allowing gas to migrate to the formations above Da'anzhai Member along fractures to accumulate or dissipate, without gas as driving force, as a result, the oil is less enriched than that in the west part of central Sichuan. © 2015 Research Institute of Petroleum Exploration & Development, PetroChina. Source


Chen S.,Southwest Petroleum University | Chen S.,Sichuan Key Laboratory of Natural Gas Geology | Lu J.,Southwest Petroleum University | Lu J.,Sichuan Key Laboratory of Natural Gas Geology | And 6 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2012

A great exploration breakthrough has been made in the bedrock, the lower part of Oligocene(E3 1) and the Paleocene and Eocene(E1+2) hanging walls of Kunbei fault-terrace belt, where an integrated oilfield with over billion tons of oils has been discovered. With the coexistence and complex distribution of bitumen and crude oils, degrees of crude oil enrichment in this area are different in different well fields, and the exploration effect of the Well Qie-4 area in the middle was relatively poor. The biomarker correlation of source rocks, crude oils and bitumen shows that oils and bitumen in Kunbei have different origins. The crude oil was derived from the upper part of Oligocene(E3 2) mature-stage source rock in Zhahaquan sag, while the bitumen originated from the E3 1 source rock and it has been destroyed and densified during the low evolutionary stage. Based on analyses of crude oil properties, microscopic fluorescence of reservoirs and reservoir inclusions, and combined with evolutionary features of source rocks and their structures, we confirmed that there are two stages of reservoir-forming in Kunbei area, which are the early Miocene(N1) and the reservoir-forming stage after the late Pliocene(N2), respectively. The current oil in the reservoirs mainly came from the second stage. The oil from the first stage mainly migrated laterally along unconformities between bed rocks and overlying sedimentary layers to form reservoirs. Because the paleo-tectonic location of the Qie-6 and Qie-12 well fields was higher than the Qie-4 well field, the scope of reservoir formation in the former was larger while compared with the latter, and its dimension of bitumen formed by later destruction was also huger. The oil from the second stage migrated firstly along the Kunbei faults to hanging walls, then laterally along unconformities and finally along main secondary faults to accumulate in the present traps. Consequently, the main secondary fault is a key factor to control the crude oil migration and accumulation. And the poor exploration effect of the Well Qie-4 area was primarily attributed to its location far away from the east fault of the Qie-16 well and disconnection of the E1+2 reservoir with the Qie-163 well field. Source

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