裂缝性致密砂岩气藏水相毛管自吸调控

钻井、完井、增产改造工作液滤液、边底水或凝析水在井筒或裂缝面附近发生毛管自吸行为和滞留效应诱发水相圈闭损害,妨碍气藏的及时发现、准确评价和经济开发.以我国四川、鄂尔多斯盆地典型致密砂岩气藏为例,基于致密气藏天然气产出机理,分析了致密气藏经济开发的水平井钻井完井、水力压裂、采气等作业环节中水相自吸过程及其对作业效果的影响.钻井完井过程中水相快速自吸进入基块,驱替出非润湿相油气,打破裂缝壁面力学—化学平衡,诱发井壁失稳；进入裂缝的工作液要快速返排,以免自吸侵入基块降低基块—裂缝传质效率；裂缝中水相高速流动,不易毛管自吸进入基块,造成边底水沿裂缝快速推进,造成水淹.矿场工程技术实践证明,裂缝致密气藏勘探开发全过程,选用合理水基工作流体体系,改善采气工艺措施,调控毛管自吸,进而达到防治水相圈闭损害的目的,是经济开发致密气藏的关键.

Aqueous Capillary Imbibition Behavior Management in Fractured Tight Gas Reservoirs

The filtration of drilling, completion and stimulation fluids, edge water and bottom water can spontaneously imbibe into and be blocked in the matrix adjacent to wellbore and fractures, which induces water phase trapping damage, preventing gas reservoir from identification, accurate assessment and economic development. The imbibition phenomena of tight sandstone gas reservoirs in west Sichuan basin and north Ordos basin during horizontal well drilling and completion, hydraulic fracturing and gas production operations are investigated on the basis of the production mechanisms of tight gas. The analysis of effects of well operation exerted by water phase imibibiton indicates that the water rapidly imbibes into matrix and displaces oil and gas, which breaks the chemical and mechanical balance and induces the borehole instability, that working fluids invading into fractures should return as soon as possible in case they imbibe into matrix and damage the fracture face, and that water proceeding along the fracture fast in fracture can be difficult to imbibe into matrix and induce waterflooding during gas production. The practices in oilfields fully prove that capillary imbibition management by optimizing water-based fluids and improving technical measures of gas production are and will be playing increasing role in preventing water phase trapping damage and economically developing fractured tight gas reservoirs.