水驱气藏水侵预测经典经验关系式lnω=BlnR的适用性分析

Applicability analysis on classical empirical relation lnω=BlnR of water invasion prediction for water drive gas reservoirs

东海已开发接近废弃的水驱砂岩气藏实际动态表明,被国内学者和现场油藏工程师广泛引用的水驱气藏水侵预测经典经验关系式lnω=BlnR并不完全符合气藏开发全过程。为此将水驱气藏物质平衡方程式与Fetkovich解析水域模型相结合,采用试算法实现了二者相互匹配条件下的水侵预测。采用本文试算法对水驱气藏水侵预测经典经验关系式的适用性进行了分析,结果表明经验关系式的适用条件与气藏水体倍数、采气速度、产量变化情况存在密切关系:水体倍数越大、采气速度越高,经验关系式适用的采气程度范围越宽;水体倍数有限、控制采气速度生产时,经验关系式仅适用于开发早期的短期预测;如果开发过程中进行了产量调整,将引起视相对压力与采出程度关系曲线上翘或下弯,经验关系式将不再适用。本文研究成果对水驱砂岩气藏水侵预测方法选择及水侵预测关系式的应用具有重要借鉴意义。

The actual dynamic data of water dri-ve sandstone gas reservoir which is to be abandoned in the East Chi-na Sea show that the classic empirical relation lnω=BlnR of water invasion prediction widely used by domestic re-searchers and engineers is not applicable for the whole development process of gas reservoirs. In this paper, the material balance equation of water drive gas reservoir is combined with Fetkovich analytical model,and the water invasion under the matching condition of the two methods is predicted with trial method. The applicability of clas-sical empirical relation of water invasion prediction for water drive gas reservoir is studied with the tria.1 method, and the results show that the applicable conditions of empirical relation are closely related to water body multiples, gas production rate and variation of gas production rate. The larger the water body multiples and gas rate are, the broader the application range of the classical empirical relation for gas reservoir would be. When water body multiples are finite and gas production rate is restricted, the classical empirical relation can only be used in the initia.1 stage for a short term. When production rate is adjusted, the curve of relative pressure and recovery degree will deform, and the classical empirical relation cannot be used. The research results provide reference to select water invasion prediction methods and apply water invasion prediction empirical relation for water drive sandstone gas reservoirs.