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

The Natural Gas Well LX-Y in the deep coal measure of Linxing area actually produced water at the rate of 82.97 m³/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 m³/d to 394 m³/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.