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Ju B.,China University of Geosciences | Ju B.,Key Laboratory of Geological Evaluation and Development Engineering of Unconventional Natural Gas Energy | Ju B.,Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism
Journal of Petroleum Science and Engineering | Year: 2014

Formation deformation of oil reservoirs is a widespread phenomenon for unconsolidated or abnormal high-pressure formations due to the depletion of reservoir pressure in the process of oil recovery. It may not only result in formation damage, but also have an adverse influence on production performance. In this paper, the deformation behavior of formation and formation damage are analyzed by elastic, elastic-plastic and plastic theory of solid porous media, and a set of expressions is derived to describe the change in porosity and permeability caused by linear or nonlinear deformation. Based on the comprehensive study on deformation of reservoir rock and multiphase flow in porous media, a new three dimensional and three phase-flow mathematical model that is used to predict the changes of porosity and permeability is presented, and the model is solved by the finite-difference method and self-adaptive iterative technique. A field-scale numerical simulator written in FORTRAN code is developed to predict the change trend of porosity and permeability in elastic and elastic-plastic deformation range.The runs of an oil field example with five-spot patterns are calculated on the simulator, and the formation damage and its influence on the pressure profiles in the vicinity around production well are studied under the condition of linear and nonlinear deformation of a reservoir. This work implies that the deformation of oil formation may be elastic, elastic-plastic or plastic in actual oil formation during the oil exploitation. The declines of porosity and permeability induced by the deformation are completely recoverable only for elastic deformation. Furthermore, elastic-plastic and plastic deformation may occur in the vicinity of production wells in unconsolidated formations. It is found that the increase of deformation coefficients presented in this work results in a sharp pressure-drop funnels on the vertical cross profile, which can be interpreted by the permeability decline induced by rock deformation. © 2014 Elsevier B.V.

Ju B.,China University of Geosciences | Ju B.,Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism | Fan T.,China University of Geosciences
Petroleum Science and Technology | Year: 2012

The experiments validate that the wettability of reservoir rocks changes from weak water wetness to strong water wetness during secondary oil recovery. The relative permeabilities of the oil and water show that the increase in water wetness results in an obvious decrease in the water permeability. A numerical simulator considering wettability alteration was developed to predict oil production. The simulation indicates the wettability alteration during water flooding has strong effects on the water cut and oil recovery. It is found that the increase in water wetness during water flooding leads to a higher oil recovery and less accumulated production water at a water cut. © 2012 Taylor & Francis Group, LLC.

Zhang X.T.,Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism | Zhang X.T.,China University of Geosciences | Zhao H.J.,Yangtze University | Yu Q.,No. 1 Drilling Company | Hu J.J.,Yangtze University
Petroleum Science and Technology | Year: 2013

The source rocks of 20 oils in Eocene reservoir from Lengdong oil field have been evaluated using geochemical biomarkers. Most of the oil samples have been undergone light to moderate biodegradation and four of these oil samples suffered heavy biodegradation. The oils were originated from low maturity source rocks within early to middle oil window according to the thermal-maturation- dependent biomarker ratios. Source-related biomarkers indicated that the oils originated from carbonate source rock possessed both high plants and algae organic matter input, while high plants' input was dominant in almost all the oils. The source rocks concerning the oils were deposited under anoxic to suboxic (low EH), salinity to hypersaline, and lacustrine environment with deep water. © 2013 Copyright Taylor and Francis Group, LLC.

Zhang F.,Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism | Zhang F.,China University of Geosciences | She Y.,Yangtze University | Zheng Y.,CAS Research Center for Eco Environmental Sciences | And 4 more authors.
Applied Microbiology and Biotechnology | Year: 2010

Currently, molecular biologic techniques achieve a great development in studies of soil samples. The objective of this research is to improve methods for microbial prospecting of oil and gas by applying cultureindependent techniques to soil sampled from above a known oil and gas field. Firstly, the community structure of soil bacteria above the Ban 876 Gas and Oil Field was analyzed based on 16S rRNA gene clone libraries. The soil bacteria communities were consistently different along the depth; however, Chloroflexi and Gemmatimonadetes were predominant and methanotrophs were minor in both bacteria libraries (DGS1 and DGS2). Secondly, the numbers of methane-oxidizing bacteria, quantified using a culture-dependent procedure and culture-independent group-specific real-time PCR (RT-PCR), respectively, were inconsistent with a quantify variance of one or two orders of magnitude. Special emphasis was given to the counting advantages of RT-PCR based on the methanotrophic pmoA gene. Finally, the diversity and distribution of methanotrophic communities in the soil samples were analyzed by constructing clone libraries of functional gene. All 508-bp inserts in clones phylogenetically belonged to the methanotrophic pmoA gene with similarities from 83% to 100%. However, most of the similarities were below 96%. Five clone libraries of methanotrophs clearly showed that the anomalous methanotrophs (Methylosinus and Methylocystis) occupy the studied area. © 2010 Springer-Verlag.

Mingjian W.,China University of Geosciences | Mingjian W.,Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism | Dengfa H.,China University of Geosciences | Dengfa H.,Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism | And 3 more authors.
Petroleum Exploration and Development | Year: 2011

This paper analyzes the Upper Palaeozoic gas accumulations and conditions of the study area by using the definition and method of petroleum system, and summarizes the natural gas accumulation pattern. The Upper Palaeozoic natural gas in the Yimeng Uplift is mainly from source rocks of Taiyuan and Shanxi Formations in the southern part and Wushenqi area. Braided channel sandbodies of alluvial fan, river channel sandbodies and distributary channel sandbodies of delta plain in the Shanxi and Xiashihezi Formations are the most favorable reservoirs. The thick mudstone layers of the Shangshihezi and Shiqianfeng Formations which cover the whole region constitute the regional seal rock, and there are also many local seal rocks. Oil source, reservoir and seal rocks form a good relationship in time and space and they form two types of assemblage which are the self-generating and self-preserving assemblage in the southern part of the Yimeng Uplift and the lower-generating and upper-preserving assemblage in the southern and northern parts. Natural gas migrated to the north through the migration pathways composed by advantageous sandbody, unconformity, faults and cracks. Structural traps and the distal accumulation pattern dominate in the northern part, while the southern part is characterized by lithologic traps and the proximal accumulation pattern. © 2011 Research Institute of Petroleum Exploration & Development, PetroChina.

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