OPTIMAL HORIZONTAL WELL PLACEMENT IN COMBINATION DRIVE THIN OIL RIM

Abstract

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.