考虑井间干扰的低渗透气藏压裂井合理井距

Rational well spacing between fracturing wells in low-permeability gas reservoirs considering interwell interference

为了确定考虑井间干扰的低渗透气藏压裂井的合理井距,以低渗透气藏压裂井为研究对象,分析了考虑井间干扰条件下的低渗透气藏压裂井流动单元内任一点处压力梯度计算公式,并推导得出不同可驱动面积比下启动压力梯度与任一点压力梯度的关系,采用非线性回归和多元线性回归数学方法,建立描述考虑井间干扰条件下的气井压裂产量递减模型,最终建立了两口压裂井间合理生产井距的计算方法。研究结果表明:①压裂井井距随储层物性、裂缝半长的增大而增大,随预期产量的增大而减小;②有效流动范围越大,合理井距越小。结论认为:①新的方法在DND气田压裂井合理井距的计算过程中效果合理,基础条件和有效流动面积比为0.9时的两口生产井井距分别为194.54 m、197.32 m;②有效渗流半径比越大,压力梯度比越小,有效面积比越大,渗流单元中有效流动面积内流体启动压力梯度应大于等于启动压力梯度;③新方法能够较准确地反映地层流体流动压力系统,该研究成果有助于低渗透气藏压裂井合理井距的确定,可以指导低渗透气藏的效益合理开发。

In order to determine rational well spacing under interwell interference,the formula to calculate pressure gradient at any point in a flowing unit of fracturing wells was analyzed under the interwell interference by taking one fracturing well of low-permeability reservoirs as an objective.And the relationship between threshold pressure gradient and pressure gradient at any point under different drainage area ratio was deduced.Furthermore,one model of production decline during fracturing,which took interwell interference into consideration,was established by means of two methods of nonlinear regression and multiple linear regression.Finally,another method for calculating the rational well spacing between two fracturing wells was developed.Results show that(1)the spacing between fracturing wells may increase with the increase of reservoir physical property and semi fracture length,whereas decrease with the increase of desired production rate;and(2)the larger the effective flow scope,the smaller the rational well spacing.In conclusion,the new method achieves reasonable effect in the process of calculating the rational spacing between fracturing wells in DND gasfield.The spacing between two production wells under basic condition and at the effective flow area ratio of 0.9 is 194.54 m and 197.32 m,respectively.The higher the effective seepage radius ratio,the lower the pressure gradient ratio and the higher the effective area ratio.The fluid threshold pressure gradient in the effective flow area of seepage unit shall be higher than or equal to the threshold pressure gradient.This method can reflect the flowing pressure of formation fluid more accurately.These are of great significance for studying the spacing between fracturing wells in low-permeability gas reservoirs and can provide effective guidance for reasonable development of these fracturing wells.