临兴地区深部煤系天然气井试采过程绒囊流体控水效果室内评价

Laboratory evaluation on the water control effect of fuzzy ball fluids in the well test process of natural gas well in deep coal measure strata of Linxing area

临兴地区深部煤系天然气井LX-Y井试采时实际产水82.97 m^(3)/d,使用绒囊流体堵水作业4 d、试采8 d后,产气量达不到预期中止。堵水后,单位生产压差产水量降幅75.8%,日产气量由300 m^(3)/d增至394 m^(3)/d,增幅31.3%,现场评价绒囊流体堵水效果出现了分歧。为了解决这一争议,室内分别以临兴盒2储层基质岩心和含人工裂缝岩心模拟层间水和人工裂缝及边底水窜产水通道,以地层水和氮气为两相流动介质,利用渗透率仪测定绒囊流体封堵后气、水两相的突破压力,模拟分析绒囊的堵水效果和稳气控水能力。绒囊流体封堵岩心基质后,水相和气相的突破压力梯度分别为0.200~0.210 MPa/cm和0.015~0.025 MPa/cm;封堵人造缝岩心后,水相和气相的突破压力梯度分别为0.035~0.040 MPa/cm和0.015~0.020 MPa/cm。结果表明,绒囊流体增加了水和气的流动阻力,但水的阻力增加更大,能够实现控水。堵水后气井产量不理想可能是地层产气能力不足、绒囊流体用量不合理等原因造成。因此,应合理调整绒囊流体体系性能和堵剂用量,增加地层水的突破压力,实现稳气控水。

The Natural Gas Well LX-Y in the deep coal measure of Linxing area actually produced water at the rate of 82.97 m^(3)/d during the well test,and after 4 days of fuzzy-ball water plugging operation and 8 days of well test,the operation stopped for the expected gas production rate was not reached.After water plugging,the water production of unit production pressure difference decreased by 75.8%and the gas production rate increased by 31.3%from 300 m^(3)/d to 394 m^(3)/d,which is not accordant with the field evaluation result on the water plugging effect of fuzzy ball.In order to settle this disagreement,this paper adopted the matrix core of He 2 reservoir in Linxing and the core with hydraulic fractures to simulate interlayer water and hydraulic fractures and edge/bottom water channeling pathways in the laboratory.Formation water and nitrogen were used as two-phase flow media.Gas and water breakthrough pressure after fuzzy-ball fluids plugging were measured by using the permeameter,and the water plugging effect and gas stabilization and water control capacity of fuzzy ball fluids were simulated and analyzed.It is shown that after the matrix core is plugged with fuzzy-ball fluid,water and gas breakthrough pressure gradient are 0.200-0.210 MPa/cm and 0.015-0.025 MPa/cm,respectively and after the core with hydraulic fractures is plugged,water and gas breakthrough pressure gradient are 0.035-0.040 MPa/cm and 0.015-0.020 MPa/cm,respectively.It is indicated that fuzzy-ball fluid increases water and gas flow resistance,but water resistance is increased more,so water control can be realized.The reasons for the unsatisfactory gas production rate after water plugging may be insufficient formation gas production capacity and unreasonable fuzzy-ball fluid dosage.Therefore,it is necessary to adjust the properties of fuzzy-ball fluid system and the dosage of plugging agent reasonably,so as to increase the breakthrough pressure of formation water and thus realize gas stabilization and water control.