Discovery of by-passed oil zone consisting of rubble split by fracture network

齐成伟

Discovery of by-passed oil zone consisting of rubble split by fracture network in tight reservoir

QI Cheng-wei

（Chongqing University of Science and Technology,   Shapingba District of Chongqing  401331）

Abstract: Compared with natural gas flowing in porous media, oil flowing in porous media does not have pressure difference resulted from volumetric expansion between interior and surfaces of rubble. Meanwhile numerical value of pressure difference is very small between upstream ‘stagnation point’ and downstream ‘stagnation point’ produced by oil or gas flowing around rubble. Thus oil flowing in pores of rubble nearly stop because of extremely small pressure gradient. Similar analysis shows that oil can hardly flow in pores in most space of narrow peninsula-like parts or those with ‘necks’. Therefore, the fracture network zone becomes a by-passed oil zone, and the recovery efficiency is inversely proportional to the coverage of the fracture network. Hence, successful ‘3D-Shattered Fracturing (3DSF)’ in shale gas reservoir can’t be applied to develop tight oil reservoir. It’s suggested that researchers should try to find more proper methods to improve single well productivity without reducing recovery efficiency.

Keywords：Mechanics of fluids in porous media; Kinematics of fluids in porous media; Shale gas reservoir; 3D-Shattered Fracturing; Recovery efficiency; Equation of state; Principle of minimum energy; By-passed oil zone

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齐成伟

Discovery of by-passed oil zone consisting of rubble split by fracture network in tight reservoir

QI Cheng-wei

（Chongqing University of Science and Technology, Shapingba District of Chongqing  401331）

Abstract: Compared with natural gas flowing in porous media, oil flowing in porous media does not have pressure difference resulted from volumetric expansion between interior and surfaces of rubble. Meanwhile numerical value of pressure difference is very small between upstream ‘stagnation point’ and downstream ‘stagnation point’ produced by oil or gas flowing around rubble. Thus oil flowing in pores of rubble nearly stop because of extremely small pressure gradient. Similar analysis shows that oil can hardly flow in pores in most space of narrow peninsula-like parts or those with ‘necks’. Therefore, the fracture network zone becomes a by-passed oil zone, and the recovery efficiency is inversely proportional to the coverage of the fracture network. Hence, successful ‘3D-Shattered Fracturing (3DSF)’ in shale gas reservoir can’t be applied to develop tight oil reservoir. It’s suggested that researchers should try to find more proper methods to improve single well productivity without reducing recovery efficiency.

Key words：Mechanics of fluids in porous media; Kinematics of fluids in porous media; Shale gas reservoir; 3D-Shattered Fracturing; Recovery efficiency; Equation of state; Principle of minimum energy; By-passed oil zone