Study On Drilling Fluid System Of Horizontal Well In Non - Conventional Gas Reservoir In

Chuanxixuwu has the characteristics of high pressure, buried depth, poor physical property, high shale content, mud shale porosity, fractures. And the actual drilling of multiple wells leak occurred repeatedly. In long horizontal drilling, suitable drilling fluid is necessary to solve wellbore wall stability, drag reduction antifriction and removing cuttings bed problems.According to the geological features of Chuanxixuwu, the demand analysis of Chuanxixuwu drilling fluid, this paper finally chose the water-in-oil drilling fluid. On the basis of the research on the mechanism of oil-based drilling fluid, the collected single dose of oil-based drilling fluid treating agent was optimized according to the type and optimum dosage range. The performance of oil-based drilling fluid is mainly affected by the emulsifier, organic soil, fluid loss agent. Therefore, after determining the scope of the optimal amount of single agent, we according to the four factors desigened four factors and three levels orthogonal experiment. The formulation of water-in-oil drilling fluid system was ultimately determined by the orthogonal test, and its properties were evaluated.This drilling fluid system has good rheological property, still maintaining good rheological properties after150℃ageing72h. The drilling fluid system pollution resistance is strong, when the water influx rate was15%, demulsification voltage is still up to961V; When adding15%NaCl pollution, the rheological properties of the system is good; While adding20%cuttings powder pollution, drilling fluid performance is still manageable. In this paper, we evaluated the plugging effect of drilling fluid by the method of measuring core permeability. The core permeability decreased98.2%through the drilling fluid contaminated, indicating that the drilling fluid has good sealing performance. The drilling fluid permeability recovery value is88.74%on average, so it can well protect the reservoir.In order to reduce the oil-based drilling fluid pollution to the environment and reduce the cost, in this paper, the oil-based drilling fluid cuttings (referred to oil-based drill cuttings) processing technology were studied. Research showed that after the cuttings dryers processing cutting oil content can be up to5%-8%, through improving experimental equipment DT5-2by low-speed desktop centrifuge indoor, we investigated the separate effect of cuttings dryer. In addition, through the analysis of drying machine technical parameters, the low price domestic powder coal dewatering machine parameters were optimized that reduced the cost.The oil-based drilling fluid system in Chuanxixuwu505H well had been applied. The application of the oil-based drilling fluid solved the problem of wellbore stability, played a role in reducing friction drag, met the on-site drilling and other special operations construction needs; Drilling, tripping, logging, casing and other operations are carried out smoothly. Compared with the previous Chuanxixuwu HF-1and HF-2horizontal wells, the new505H had created five indicators Xuwu horizontal wells index.