A novel model for oil recovery estimate in heterogeneous low-permeability and tight reservoirs with pseudo threshold pressure gradient

Energy Reports

Fei Yi¹  Mingda Dong²  Xiaofeng Zhou²  QingLong Zheng²  YuWei Chen³  Jiangtao Li³  Huang Bo³  Xuedong Shi⁴  Jianguang Wei⁴  Dongmei Zhang⁵  Yuhan Yin⁶ 

[1] Corresponding author.;Production Co, China;;Cnooc Enertech-Drilling &Institute Of Unconventional Oil&Gas, Petroleum Engineering Department, Northeast Petroleum University, China;PetroChina Tarim Oilfield Company, China;Petroleum Production Engineering Technology Research Institute of Huabei Oilfeld Company, China;

关键词: Low-permeability and tight reservoirs;    Pseudo threshold pressure gradient (PTPG);    Permeability heterogeneity;    Oil recovery factor;    Coefficient of permeability variation;   

DOI  :  

来源: DOAJ

【 摘 要 】

Pseudo threshold pressure gradient (PTPG) is one of the main factors affecting the oil recovery of heterogeneous low-permeability and tight reservoirs. When the pressure gradient between the supply boundary and the bottom hole is less than PTPG, the crude oil in the formation cannot flow. In order to accurately measure the relationship between PTPG and permeability, a novel experimental device has been designed and a series of core flooding experiments using brine and oil have been carried out. The new experimental device eliminates the influence of rubber sleeve in core holder and core end-effect on the results, and greatly improves the accuracy of pressure measurement. The experimental results show the PTPG has a power function relationship with permeability, and has no obvious relationship with the viscosity of the fluid. Based on the equation for PTPG and permeability of crude oil and brine fitted by the experimental data, a new heterogeneous reservoir mathematical model considering PTPG were established. The influence of the coefficient of permeability variation, average permeability, and the production rate on oil recovery factor have been studied by this model. The results clearly show that the coefficient of permeability variation has the greatest influence on oil recovery factor, which represents inhomogeneity in low-permeability and tight reservoirs. Also, when the coefficient of permeability variation is less than a certain value (about 0.2 when average permeability is 1mD, in our model), there is only a slight decline in oil recovery factor, and when coefficient of permeability variation is larger than this value, the oil recovery factor decreases rapidly. The finding is consistent with oil field production and helpful to determine whether to take EOR(enhanced oil recovery) measures for a low-permeability heterogeneous reservoirs.

【 授权许可】

Unknown