Experimental Study Of Oil-Based Gel For Lost Circulation Control

During the oil and gas exploration process,lost circulation is one of the main factors that affect the drilling cycle and reduce the exploration and development effect.If there is no effective lost circulation control method,it will bring huge economic losses to the oil and gas production.Oil-based drilling fluid has been widely used in oil field drilling with the advantages of high temperature resistance,calcium contamination resistance and good lubricity.But the conventional lost circulation material used in oil-based drilling fluid cannot be effectively plugging leakage formation.Therefore,to resolve this problem of lost circulation,a new kind of oil-based gel as plugging materials was developed in this paper.Based on the comprehensive review of lost circulation resistance and control technique at home and abroad,the basic experimental scheme of oil-based gel was determined and the research of the following key techniques was completed as follows:(1)preparation of oil-based gel and study of influencing factors;(2)laboratory study of oil-based gel performance;(3)evaluation of oil-based gel plugging effect.The formulation of oil-based gel that was composed of NJZ as main gelant solution and JLJ as crosslinker was determined and optimized by experiment.The NJZ can react with JLJ to quickly form high viscosity gel in high pressure line.Then after the oil-based gel entered leakage formation,the viscosity of gel can increase to more than 104mPa·s,which can effectively plug leakage formation.The newly developed oil-based gel has good temperature resistance and very high strength under 150?.The oil-based gel showed good plugging ability for fracture with different size.It was found that injection by repeatedly squeeze of gel can has better plugging ability.The breakthrough pressure of gel can reach 0.7 MPa/m for plugging fracture with 1mm width,which indicated the gel had good plugging efficiency.