海上异常高压气藏应力敏感特征及产能方程——以莺歌海盆地为例

目前国内外推导的异常高压气藏考虑应力敏感效应的产能方程中混淆了有效应力与生产压差的概念。为此,在前人研究的基础上,通过对实验和产能测试资料的分析,探讨了应力敏感对储层物性和气井产量的影响问题,并基于修正的应力敏感方程,结合气藏渗流特征,重新建立了符合油气藏地质特征的新的二项式气井产能方程,从理论上阐述了莺歌海盆地异常高压气藏产能特征,并用实际测试资料检验了该方程的实效性。结果表明,莺歌海盆地异常高压气藏开发中不应忽视应力敏感效应,在同一储层特征条件下,应力敏感效应特征越显著,开发过程中表现出的应力敏感效应越严重,气井产能损失就越大。因此,在异常高压气藏生产管理中,应采取合理的开发技术手段和工作制度,防止井筒附近地层压力迅速下降导致储层渗透能力及气井产能的下降。所取得的成果、认识可推广应用于其他类似探区。

Stress sensitivity features and productivity equations of offshore abnormal high-pressure gas reservoirs: A case study from the Yinggehai Basin

At present scholars often mix up the concepts of effective stress and drawdown pressure, especially when the stress sensitive productivity equations for those overpressure gas reservoirs are applied. Based on the previous studies and data analysis on the stress sensitive experiments and production tests, the effects of stress sensitivity on reservoir physical properties and gas well production are discussed. Furthermore, a new binomial equation of gas well productivity suitable for the geological features of a hydrocarbon reservoir is reformulated on the basis of the amended stress sensitivity equation and the percolation characteristics of a gas reservoir. The new binomial equation theoretically indicates the productivity features of abnormal high pressure gas reservoirs in the Yinggehai Basin, and its effectiveness is validated through actual test data. The results show that the stress sensitivity effect should never be ignored in the development of abnormal high pressure gas reservoirs in the Yinggehai Basin; the more obvious the stress sensitivity on the same gas reservoir, the greater the stress sensitivity effect during the development and the greater loss in gas well productivity. Therefore, a reasonable working system and development technology means should be implemented to manage the production of abnormal high pressure gas reservoirs and to avoid rapid dropping of formation pressure around the wellbore which contributes to the reduction of reservoir permeability and gas well productivity. This study is practical and helpful in other similar reservoir development projects.