页岩气井间干扰分析及井距优化

Interwell-production interference and well spacing optimization in shale gas reservoir

页岩气井距设计与优化是评价页岩气开发效果的重要指标。在理论认识的基础上,根据类比法、数值模拟、经济评价方法论证,形成了从井间干扰模拟、动态数据诊断到多井生产模拟、井距优化的完整工作流程:①通过建立压力探测边界传播模型,模拟不同连通条件下井间干扰响应程度;②基于井间干扰响应规律,根据气井生产动态数据演绎识别、诊断井间干扰;③以地质解释和动态分析结果为基础参数,建立气藏体积压裂多井数值模型,模拟气田生产动态,结合净现值模型优化井距。以长宁国家级页岩气示范区宁201井区为例,模拟表明,减小井距可使得井间干扰提前发生,同时也提高区块整体采收率;基于目前的压裂规模和参数体系,300~400 m井距可进一步优化至260~320 m,单位面积内井数增加20%~30%,区块储量采收率提高10%左右;区块整体净现值随着生产年限不断增加,但对应的最优井距结果不随生产周期的改变而改变。

For the purpose of enhancing recovery and economics of shale resource,it is a critical task for petroleum engineers to determine the optimal well spacing in the industry development of shale play.By using various approaches including analogs,numerical simulation and economic assessment based on the theoretical understanding,this paper integrated interference response simulation based on multi-well pattern with history data matching to establish a comprehensive workflow for identifying production interference and optimizing well spacing.The workflow is threefold:firstly,a general semi-analytical model for the distance of pressure investigation was presented to calculate the interference time through fracture and rock matrix;secondly,a method of interference measurement was introduced to quantify production interference by searching for changes in buildup trends while wells are staggered on/off production;finally,a numerical model of coupling geological and fracture geometry information was proposed to optimize well spacing in multiple-well pattern with purpose of maximizing the objective function of net present value.In this paper,Ning 201 well block in Changning pilot area is taken for example,the simulation results show that①fracture conductivity is more important in short-term production period,while fracture half-length becomes more significant at long-term production period;②there is a potential of decreasing well spacing from 300-400 m to 260-320 m,with the increasing number of production wells by 20%-30%and enhancing recovery of reservoirs by 10%;③the value of NPV would increase with the production period elongating,but the optimal well spacing kept constant regardless of the duration of production period.