Liao Wei
PetroChina Xinjiang Oilfield Company, Karamay 834000, China.
ACS Omega. 2021 Nov 18;6(47):31727-31737. doi: 10.1021/acsomega.1c04419. eCollection 2021 Nov 30.
Affected by the complex operation mode of strong injection and strong production, sand production can seriously affect the life cycle and peak shaving capacity of gas storage. In this paper, combined with the actual production situation of China's largest gas storage (H Gas Storage), the effect of the gas flow rate, production pressure difference, formation pressure drop, permeability, and water saturation on sand production was systematically analyzed via an indoor sand production simulation experiment. The results showed that from the initial flow rate of 1.88 L/min to a critical flow rate of 3.87 L/min, the core permeability and the stage sand production continued to increase; however, during the flow rate from 3.87 to 8.58 L/min, the core permeability and the stage sand production decreased gradually. The whole process showed that only a small amount of free sand was produced in the early anhydrous production stage. Proper sand production in this stage can make the rock permeability and the gas production grow to a certain extent. But when the gas flow rate reached 3.87-8.58 L/min, pore throats were blocked by sand particles of large sizes. When all sand particles were carried away by the gas flow, no sand production occurred and the rock permeability remained unchanged. In this experiment, the critical pressure difference was 5 MPa. Under the same production pressure difference, the greater the rock permeability, the greater the stage sand production; similarly, under the same rock permeability, the greater the production pressure difference, the greater the stage sand production. In the case of high rock permeability, sand production occurred when the displacement pressure difference was 2 MPa. For the formation pressure drop, sand production occurred when the effective stress reached 10 MPa; furthermore, when the effective stress reached 16.5 MPa, the stage sand production reached the largest value; finally, when the effective stress reached 28 MPa, no sand production occurred anymore. Sand production was easy to occur in cores containing water, which was related to the hydration and swelling of clay minerals, the increase of seepage resistance in gas-water two-phase fluids, and the increase of shear stress in pore throats.
受强注强采复杂运行模式影响，出砂会严重影响储气库的生命周期和调峰能力。本文结合我国最大储气库（H储气库）实际生产情况，通过室内出砂模拟实验，系统分析了气体流速、生产压差、地层压降、渗透率和含水饱和度对出砂的影响。结果表明，从初始流速1.88L/min到临界流速3.87L/min，岩心渗透率和阶段出砂量持续增加；然而，在流速从3.87L/min到8.58L/min过程中，岩心渗透率和阶段出砂量逐渐降低。整个过程表明，在无水采气初期仅产出少量游离砂，此阶段适当出砂可使岩石渗透率和产气量在一定程度上增长。但当气体流速达到3.87 - 8.58L/min时，大尺寸砂粒堵塞孔喉，当所有砂粒被气流携带走后，不再出砂，岩石渗透率保持不变。本实验中临界压差为5MPa，在相同生产压差下，岩石渗透率越大，阶段出砂量越大；同样，在相同岩石渗透率下，生产压差越大，阶段出砂量越大。在岩石渗透率较高情况下，当驱替压差为2MPa时发生出砂。对于地层压降，当有效应力达到10MPa时发生出砂；此外，当有效应力达到16.5MPa时，阶段出砂量达到最大值；最后，当有效应力达到28MPa时，不再出砂。含水泥心中易发生出砂，这与黏土矿物的水化膨胀、气水两相流体渗流阻力增加以及孔喉处剪切应力增大有关。
