Research On Borehole Wall Stability And Plugging Drilling Fluid Technology In Yan Chang Oilfield

With the constant improvement of the oil and gas drilling technology, sidewall instability has become the main technical difficulty in drilling engineering,and still didn’t get very good solve. Hole drilling, downhole in stress equilibrium state, after the borehole drilling, drilling fluid column pressure in oil Wells are replaced by drill of borehole wall rock support, destroyed the original formation strata balance, thus caused the sidewall instability.This paper researchs the factors affecting the stability of borehole wall, and gives the formation pore pressure, leakage pressure and collapse pressure and fracture pressure calculation method, to study the distribution rule of the layers of a fracture pressure. According to the above method to determine the extension of the oil field of 26 Wells formation collapse pressure equivalent density and equivalent density of formation fracture pressure.On this basis, through the experiment to evaluate different plugging agent, optimizing the good performance of drilling plugging agent FLO- 3, it is concluded that added 1 ~ 3% FLO-3 while drilling plugging agent system of drilling fluid, the permeability loss and 0.5 mm has good plugging effect, the microfracture loss bearing capacity can reach more than 10 MPa. Field test showed that after joining plugging agent with drilling fluid leakage is decreased obviously, and basic in the late homework is only a small amount of filtration, filling water rarely, shows that the plugging drilling fluid system has played a very good plugging effect.