Experimental Study Of Sealing Capability Of Trap Caps In Gas Reservoirs: Taking The Hutubi Gas Storage As An Example

The evaluation of trap sealing of gas reservoirs can reduce investment and oil and gas development risks. In this paper, taking the Hutubi gas storage as an example, we used the breakthrough pressure experiments, uniaxial and triaxial rock mechanics experiments, and acoustic emission experiments to systematically evaluate the sealing ability of the trap caps. The research results show that a set of mud stones of the Anjihaihe Formation is developed in the upper section of the Ziniquanzi Formation, which is a stable regional caprock in this area. The breakthrough pressure of the cap rock in this area is between 2.0 MPa and 3.0 MPa, so the height of the air column that can be sealed is greater than 200 m, and thc undulation of the trap is only 180 m, which is less than the height of the air column that can be scaled, Therefore, thc mudstonc cover of this study is very effective for reservoirs. The reverse faults in thc study area have good vertical plugging properties. The mudstone smearing factor SSF of the Hutubi fault in the Ziniquanzi Formation is 1 similar to 3.3, which is less than the lower limit of plugging 7. Therefore, thc fault has good lateral plugging performance. The average dynamic breakthrough pressure of thc gas driven oil in the Hutubi cap layer is 5.1 MPa, which has a good capillary sealing ability. The results of triaxial compression experiments show that the average compressive strength of the cap layer is 92 MPa, and the average value of the cumulative plastic strain of alternating stress for 50 cycles is 0.14%, which is obviously lower than the critical index of cumulative plastic strain of 1% under fatigue failure. The final evaluation results concluded that the risk of fatigue failure of the caprock studied was low, and the caprock of the gas reservoir had good petrophysical sealing properties and mechanical integrity.