洼38块薄层水平井蒸汽吞吐产量递减规律分析及开发对策

Production Decline Law Analysis and Developing Countermeasures for Steam Drive by Thin-layer Horizontal Well in Wa38 Block

为进一步提高油藏动用程度,洼38块从2006年起在薄油层区域部署水平井,并采用油层酸化、井筒电加热等措施辅助蒸汽吞吐开采。然而,洼38块薄层水平井蒸汽吞吐采油呈现阶段峰值产量高、产量递减快的特征。采用扩散方程加定解条件的方法,建立了水平井渗流数学模型,推导出了在拉普拉斯空间中水平井的无因次产量与无因次井底压力之间的关系式,并作出理论上封闭油藏中不同影响因素下水平井的产量递减曲线,得出主要产油阶段在峰值期的结论。据此制订了调整措施,即在保证不出砂的前提下,尽量提高采液强度,趁热快采,提高热利用效率,进而提高油汽比,从而达到增产的目的。水平井洼38-东H3在第3周期后应用了该措施,第4周期油汽比从0.27上升到0.6,第5期的油汽比也比第3周期高0.08,取得较好的增产效果。

In order to improve reservoir recoverable degree,horizontal well is drilled in thin-layer area of Wa38 block since 2006,and acidizing and electric heating on borehole helped to steam drive.In production,the steam drive in this block has the characteristics of high production of phase peak value and quick decline of the production.The method of diffusion equation under definite condition is applied to build a mathematic flow model for the horizontal well.A relational expression between dimensionless rate and dimensionless bottom hole pressure of the horizontal well in Laplace space was derived.Production decline curves of the horizontal well were drawn under different influencing factors in bounded reservoir on theory.A conclusion is drawn：the main oil production is at peak stage.According to that,the adjustment measure is taken：under the precondition of ensuring no sanding,liquid production per unit thickness and efficiency of heat utilization should be increased,and then the goal of stimulation will be achieved with the enhanced oil/steam ratio.The measure is taken in Wa38-dong H3 horizontal well after three cycles.The results are good with the oil/steam ratio enhanced from 0.27 to 0.6 at fourth cycle and increased by 0.08 than third cycle in fifth cycle.