川东石炭系气藏开发方式对采收率的影响及技术对策

Influence of development mode of carboniferous gas reservoir in East Sichuan on gas recovery and technical countermeasures

川东石炭系气藏非均质性较强,渗透率差异较大,部分区块水侵影响较严重,气藏处于开发中后期,如何提高采收率已经成为一个重要课题。气藏的采收率受到地质因素及开发因素的双重影响,地质因素是气藏固有特征,决定气藏品质,开发因素决定现有技术条件下对气藏的开采效果。为了提高川东石炭系气藏采收率,在地质特征基础上,通过模拟不同开发方式对采收率的影响,分析开发效果并提出技术对策。分析结果表明:条带状、椭圆状气藏开发井网应先沿构造轴线高部位线形布井,再向气藏边翼部呈“之”字型布井;近等轴状气藏开发井网部署应遵循“网格状”均匀布井的原则;低渗透储量应以水平井或大斜度井开发,水平井合理井距应控制在1000 m左右;水平井的实施效果与储层物性相关,水平井应尽量避免部署在易出水的区域;无边水、底水气藏的开发规模越大,气藏采收率越高,但是有边水、底水气藏,较大的开发规模会导致边水推进、底水锥进,反而无法提高采收率;合理的废弃条件可以实现产量及效益双增加。

The carboniferous gas reservoirs in East Sichuan has strong heterogeneity,large permeability difference,and some blocks are seriously affected by water invasion.The gas reservoirs are in the late stage of development,how to improve gas recovery has become an important topic.The gas recovery is affected by both geological factors and development factors.Geological factors are the inherent characteristics and determine the quality of gas reservoir.Development factors determine the production effect under the existing technical conditions.In order to further improve the gas recovery,based on the geological characteristics,by simulating the impact of different development mode on recovery,the development effect is analyzed and technical countermeasures are provided for enhancing recovery.The analysis results show that,the well pattern of strip and oval gas reservoirs should follow the linear layout of wells along the high part of the structural axis,and then forming“zigzag”well pattern from top to edge;the well pattern of near equiaxed gas reservoir should follow the principle of uniform well distribution;low permeability reserves should be developed by drilling horizontal wells or highly deviated wells,the reasonable well spacing should be controlled at about 1000 m;the effect of horizontal well is related to reservoir physical properties,the well location should be avoided in the area easy to produce water;for gas reservoirs without edge and bottom water,the larger the gas production is,the higher the gas recovery is,but for gas reservoirs with edge and bottom water,the larger gas production will lead to edge water propulsion and bottom water coning,it can not improve the gas recovery;reasonable abandonment conditions should be selected to realize the double increase of production and benefit.