The Research And Application Of Water Based Drilling Fluid For Shale Gas In Weiyuan

In order to solve the tight situation of the domestic oil and gas resources, increase of shale gas exploration and development efforts is the trend of development. Just a few years, China has built several large-scale pilot, developed quite rapidly. In view of the successful experience of the development of shale gas in the United States, Oil-based drilling fluid is mainly used in the construction of domestic shale gas horizontal wells, but the high cost and pollution is the natural defects, and has adverse effect on HSE(Health, Safety, Environmental). Therefore, it is necessary to study the water-based drilling fluid to solve these problems.The lost circulation, collapse, tight hole, friction, cutting carrying, contaminate formation and other issues, which are happened greatly increase because of many cracks in the shale formation which is sensitivity to water. Especially in the level of long horizontal wells. Therefore, the key is wellbore stability, friction, cutting carrying for the construction of water-base drilling fluid in shale gas horizontal well.This paper described the inhibition of XJA-1 which is the core agent, ang screening and evaluation other agents, and form the drilling fluid formula. Laboratory evaluation proved that can tolerable 160℃ when the density is 2.0 g/cm3, which can resist more than 10% of the clay pollution, and more than 5% of the salt water pollution. In sand bed experiment, 30 min has no filtration, and the invasion depth is only 2.5cm, this proved the sealing performance is good. The friction coefficient is less than 0.08 before and after the aging reaction, the lubrication performance is good. The permeability recovery value is greater than 87%, which can effectively protect the reservoir. Field tests show that the drilling rate is during 3 and 6 m/h, and the average well diameter is 12.73% when use the new drilling fluid system. Although it is less than oil based drilling fluid, but showed good lubricity and inhibition. It can meet the basic requirements of site construction.Compared with the oil base drilling fluid, it can reduce the cost of nearly 30%, and cutting oil content is lower, reduce the harm to the environment. It has broad application prospects.