A New Method of Calculating Water Invasion for Heavy-Oil Reservoir by Steam Injection

摘要

Heavy oil production methods included the cyclic steam stimulation (CSS), steam flooding and steam assistant gravity drainage (SAGD). It is well known, when water invasion occurs in heavy oil reservoirs with edge/bottom water, for a long time, how much of the produced water comes from the steam injection process as oppose to edge/bottom water invasion? Reservoir engineers do not clearly understand the process, because after the steam condenses a part of the condensation comes to the surface and another part is stored within the reservoir itself. This is the problem that still gives reservoir engineers trouble. Through studying the production data of thermal recovery at the Liaohe oilfield, in China, for the first time, this paper reveals a new theory and calculation method that shows how to calculate water invasion from the bottom/edge water reservoir, therefore, a new concept of conversion rate was presented and a new parameter of steamwater ratio was defined, as k. new equations of calculating produced water invasion and water invasion of the remaining formation with bottom/edge water were derived according to the new parameter k. In addition, an estimation method of breakthrough time of bottom/edge is presented in this paper. The methods have been used to calculate and analyze the production performance of heavy oil with steam injection in Liaohe oilfield. The calculation results accord well with actual situation of heat-recovery reservoirs. Therefore, this method will be recommended to optimize production performance parameters of thermal recovery.