关键词: 实验分析技术, 致密油储层, 芦草沟组, 二叠系, 吉木萨尔凹陷, 准噶尔盆地

Abstract:

 Critical rate of horizontal well in gas cap and bottom water reservoirs is an important factor to measure whether the water and gas had breaked through oil-well earlier or not, so calculating its value accurately is of great significance during developing the gas cap and bottom water reservoirs. Based on the cresting mechanism of bottom water and gas cap around bore hole of horizontal well, this paper considered the ellipsoid constant pressure surfaces as family of the rectangles, used the principle of elliptical flow to deduct a new model for calculating the critical rate of horizontal well in gas cap and bottom water reservoirs. Through actual calculation and contrast, the result calculated by new model only has a small relative error with that calculated by numerical simulation method, only 9.08%. Moreover, when the reservoir thickness is big enough, the error will become smaller, which demonstrates that the new model has higher accuracy and practicability. Sensitivity analysis shows that with the increasing of dimensionless wellbore location, the critical rate presents increasing early, but decreasing when the dimensionless wellbore location has reached a high value. The critical rate gets maximum value when the dimensionless wellbore position is 0.4 because of the physical character differences between gas and water. So during developing the gas cap and bottom water reservoirs with horizontal well, it would be best to prefer the horizontal wellbore location so as to keep higher critical rate.

Key words:  experimental analysis technology, tight reservoirs, Lucaogou Formation, Permian, Jimsar Sag, Junggar