OPTIMAL HORIZONTAL WELL PLACEMENT IN COMBINATION DRIVE THIN OIL RIM

Producing from thin oil rim reservoirs has always been a challenge in oil and gas industry, due to problems related with early gas and water coning that usually limit oil production below commercial rates. Most of the thin oil rim reservoirs are sandwiched between an overlain gas cap and an underlain aquifer. Strategies to develop thin oil rim have been studied and implemented such as the concurrent oil and gas production as well gas blowdown after oil recovery. As thin oil rim reservoirs are susceptible to coning or cresting of gas and water, horizontal wells are preferred with the objective of maximizing oil recovery while coning tendencies are minimized. In order to maximize the oil recovery in these columns, this study investigates how horizontal well location and target liquid production rate affect oil recovery for different gas cap and aquifer sizes in a thin oil rim column with 70 ft thickness using a numerical reservoir simulator (ECLIPSE 100). Results show that the gas cap size and aquifer strengths play an important role on the increment of oil recovery. In general, the well should be located at the bottom half of the thin oil rim when the gas cap has stronger influence than water and at the upper half of the thin oil rim when the aquifer support is stronger than gas expansion. For small and moderate aquifer size (5 and 50 PV), small target liquid rates yields the highest oil recovery factor, while for larger aquifer size (500 PV) higher target liquid rate leads the highest oil recovery.

薄油环油藏的开发长期以来都是油气工业领域的一大难题，究其原因在于早期气水锥进问题通常会将原油产量压制至商业产能以下。多数薄油环油藏均夹于上覆气顶与下伏含水层之间。针对薄油环开发的各类策略已得到研究与落地应用，例如油气同采工艺以及采后放气技术。鉴于薄油环油藏极易发生气水锥进或脊进现象，因此优选水平井开发方案，以期在抑制锥进趋势的同时最大化原油采收率。为最大化此类油藏柱的原油采收率，本研究借助数值油藏模拟器（numerical reservoir simulator）ECLIPSE 100，针对厚度为70英尺的薄油环油藏柱，探究了水平井位置与目标产液速率对不同气顶规模和含水层规模下原油采收率的影响。研究结果表明，气顶规模与含水层能量对原油采收率的提升具有显著影响。总体而言，当气顶驱动作用强于水体补给时，水平井应布设于薄油环的下半区域；而当含水层补给强于气体膨胀驱动时，水平井则应布设于薄油环的上半区域。对于小型及中型含水层规模（5与50孔隙体积），较低的目标产液速率可获得最高的原油采收率；而对于大型含水层规模（500孔隙体积），较高的目标产液速率则可实现最优原油采收率。