沙特高温高压低渗凝析气井全过程欠平衡设计与应用

Total Underbalance Drilling Design and Application for HTHP Low Permeability Gas-condensate Well in Sandi Arabia

沙特B区块属于高温高压低渗凝析气田,储层为致密砂岩地层,在前期的勘探作业中,钻井中显示良好而测试时产量不高,室内实验表明油锁和水锁是引起储层伤害的主要原因。本文采用一种新型全过程欠平衡设计方法,在设计时充分考虑了井控安全、油锁、水锁、井壁稳定对井底负压值的影响、在水力参数计算过程中高温高压对钻井液密度和黏度的影响;在施工过程中考虑了在钻进、接立柱、取心、起下钻等整个作业过程中保持井底负压所需要的设备和工艺。通过现场M-0001井试验表明,该方法能有效释放油气井产能,避免储层伤害,测试后显示该井表皮系数为-3.44,钻井过程中储层没有污染。

The B block in Saudi Arabia is a High Temperature and High Pressure （HTHP） low permeability condensate gas reservoir. The early exploration wells show good behavior,but with not very high production rate. Indoor experiments show that the oil lock and the water lock are the main cause of the reservoir damage. In order to deal with this problem during the drilling operation, the underbalance drilling is adopted. In the design of the negative pressure value in the process, the well control safety, the borehole stability, the oil lock damage, the water lock damage and other factors are taken a full account with respect to their influences on the bottom negative pressure value selection under 2-10MPa while drilling. In the calculation of the hydraulic parameters, the influence of the temperature and the pressure on the drilling fluid density and viscosity is considered, the industry approved Drillbench software is used to calculate the sensitivity of the drilling fluid density, and finally to determine the drilling fluid density, which is in the range of 1.69-1.76g/cm3. The main equipment includes the rotating blowout preventer, the DDV, the automatic choke manifold, the four-phase separator, the data transmission and processing equipment, the ignition line, and the automatic ignition system. With the setting up of DDV, it is not necessary to shut down the well in the process. In the M-0001 well Sarah group, the real drilling process shows that the fluid density is in the range of 1.69-1.71g/cm3, the bottom hole negative pressure value in the range of 2.08-3.12MPa. According to the M-0001 well test data, the main reservoir skin factor S=3.44, indicating that M-0001 well drilling fluid has a good effect on the gas reservoirs, and the drilling process will not cause the formation pollution.