Well interference evaluation considering complex fracture networks through pressure and rate transient analysis in unconventional reservoirs

Severe well interference through complex fracture networks(CFNs)can be observed among multi-well pads in low permeability reservoirs.The well interference analysis between multi-fractured horizontal wells(MFHWs)is vitally important for reservoir effective development.Well interference has been historically investigated by pressure transient analysis,while it has shown that rate transient analysis has great potential in well interference diagnosis.However,the impact of complex fracture networks(CFNs)on rate transient behavior of parent well and child well in unconventional reservoirs is still not clear.To further investigate,this paper develops an integrated approach combining pressure and rate transient analysis for well interference diagnosis considering CFNs.To perform multi-well simulation considering CFNs,non-intrusive embedded discrete fracture model approach was applied for coupling fracture with reservoir models.The impact of CFN including natural fractures and frac-hits on pressure and rate transient behavior in multi-well system was investigated.On a logelog plot,interference flow and compound linear flow are two new flow regimes caused by nearby producers.When both NFs and frac-hits are present in the reservoir,frac-hits have a greater impact on well#1 which contains frac-hits,and NFs have greater impact on well#3 which does not have frac-hits.For all well producing circumstances,it might be challenging to see divergence during pseudosteady state flow brought on by frac-hits on the logelog plot.Besides,when NFs occur,reservoir depletion becomes noticeable in comparison to frac-hits in pressure distribution.Application of this integrated approach demonstrates that it works well to characterize the well interference among different multi-fractured horizontal wells in a well pad.Better reservoir evaluation can be acquired based on the new features observed in the novel model,demonstrating the practicability of the proposed approach.The findings of this study can help for better evaluating well interference degree in multi-well systems combing PTA and RTA,which can reduce the uncertainty and improve the accuracy of the well interference analysis based on both field pressure and rate data.

一种用于多级压裂水平井判别来水方向的多井干扰压力分析方法

为了确定直井注水、水平井采油的联合井网井间连通情况,建立考虑裂缝非均匀产液的多级压裂水平井多井干扰试井解释模型,运用Green函数、Newman乘积法得到井底压力解,绘制无量纲压力和压力导数典型曲线图版,进行参数敏感性分析。多级压裂水平井多井干扰试井模型典型曲线划分为7个流动阶段,其中在系统干扰流阶段,压力导数曲线下降,且注水井的注水量越大,其下降程度越大,当周围注水井的总注水量小于多级压裂水平井产量时,压力导数曲线呈阶梯状下降特征,最终表现为一条水平直线段,当周围注水井的总注水量大于观测井产量时,压力导数曲线将一直下降,呈现下掉特征;注水井到多级压裂水平井的距离越近,系统干扰流阶段持续的时间越长。实例应用表明,提出的模型能够确定注采井间连通情况、判别多级压裂水平井来水方向,指导油田开发措施的制定。

流量不均鱼骨状多分支水平井不稳定压力分析

为研究分支井和主井筒流量密度分布不均及各生产段表皮分布不均对鱼骨状多分支水平井井底压力(bottom hole pressure,BHP)的影响,通过将分支井段和水平主井筒段考虑成线源,运用格林函数并结合Newman乘积方法,建立了鱼骨状多分支水平井非均匀流量的试井解释模型,利用数值反演算法计算BHP,绘制出典型试井曲线并进行敏感性因素分析.结果表明,该模型出现了新的渗流特征段,其特征段在压力导数曲线上呈现出斜率大于0.5的直线段,将其命名为分支干扰线性流动段.鱼骨状多分支水平井分支井段及主井筒段流量不均时,BHP响应与各分支井段及主井筒段的流量以及表皮分布密切相关,同时也受到分支的长度、角度、地层各向异性、井筒在地层中高度和分支在主井筒上位置等因素的影响.该模型对鱼骨状水平井的产油井段诊断与解释、储层伤害判断以及增产措施制定有指导意义.

非均质高压气藏动态储量评价方法

非均质高压气藏动态储量评价存在两大问题:(1)对于高压气藏而言,岩石弹性能量不可忽略,不考虑岩石弹性能量计算的动态储量相对于考虑岩石弹性能量所计算的动态储量,误差高达30%;(2)储层非均质性强,连通程度存在差异导致传统物质平衡法不适应,动态储量难以准确计算。针对以上问题,结合四川盆地安岳气田磨溪区块下寒武统龙王庙组气藏的地质与动态特征,应用最小二乘法确定并评价岩石有效压缩系数;划分连通单元,根据连通单元的特点有针对性地选取相应的动态储量计算方法,形成了以连通单元的划分为基础,实测压力梯度约束下的流压折算与全生命周期压力历史拟合相结合,全生命周期不稳定试井分析法、现代产量递减分析法与异常高压物质平衡法综合应用的非均质气藏动态储量评价方法,并对不同方法的适用性及影响结果准确性的因素进行评价,为非均质高压气藏动态储量评价提供了技术参考。