During the drilling process, the density of drilling fluid will be reduced and increase the viscosity after being invaded by natural gas or air. The decrease of drilling fluid density leads to the decrease of hydrostatic column pressure, which may lead to blowout, well collapse and other malignant accidents. Therefore, the gas invasion drilling fluid is very dangerous, and measures must be taken to deal with it correctly.
After drilling to the natural gas reservoir, the gas probably invade the drilling fluid, and we are sure the air will invade the drilling fluid during the working process of shale shaker, cyclone and mud agitator. The density of drilling fluid decreases obviously after gas invasion, but the influence on the hydrostatic column pressure in the well is much smaller than people think. The reason is that the invading gas is compressible and the density of drilling fluid will increases gradually with the depth of the well. In these two case, there are 2 different pressure gas. So It is dangerous to make a decision to use weighting method to make up for the density reduction only based on the reduction of drilling fluid density that has been invaded by gas, which may lead to the excessive density of drilling fluid , fracturing the formation and polluting the production formation. It will reduce the ROP, cause leakage and lead to the decrease of liquid level in the well, and then blowout.
In order to restore the density of drilling fluid, the most effective means is to use degasser. GN solids control can provide two degasser. The normal poorboy degasser and vacuum degasser. First kind is installed before shaker. Received the drilling mud from well, and vacuum degasser installed between mud cleaner. They utilized different principle, first kind through increase touch area when mud drop on the bottom of tank, brake the bubble involved in mud and move out gas. The vacuum degasser through generate a negative pressure space to make the gas out of mud. Both kind degasser will be need in one full mud system. If you have demand, welcome to contact us.