Pre-Heating Circulation Design for Dual Horizontal Well SAGD in the Medium-Deep Extra Heavy Oil Reservoirs

Du 84 block in Liaohe oilfield is an extra heavy oil reservoir, which has a depth of 705 to 708 meters, average pay thickness of 50 to 90 meters, The current oil recovery using Cyclic Steam Stimulation (CSS) has reached 31%. Two SAGD pilots using dual horizontal wells have been constructed to test the follow-up process as the way to further improve the ultimate recovery factor. To establish the uniform heating along the new drilled horizontal wells in the partial depleted reservoir after CSS, the preheating circulation is applied during the initial stage of the pilot test. The challenge is that returning fluids from the circulation is difficult to lift to the surface due to low pressure in the formation (4-5 MPa). The presence of formation dip, which causes a relatively large projected horizontal separation (4-5 m) between the wells, further increases the difficulties for achieving uniform pre-heating. This paper presents the results from numerical simulation and reservoir engineering analysis. The downhole tubing design and operating parameters for pre-heating dual SAGD wells using circulation are determined for achieving uniform communication along the horizontal sections.