Research and Application of Cost Reduction of Deep Coal Rock Gas Drilling Fluid

China is rich in deep coal rock gas resources, and in recent years, deep coal rock gas has become a hot spot for exploration and development of unconventional oil and gas resources. Restricted by the problems of gangue collapse and frequent blocking, the cost of drilling fluid remains high, which affects the efficient development of deep-seated coal rock gas resources. Coal gangue collapse is both the focus of solving the problem of well wall instability in the horizontal section and the choke point that restricts the efficient exploration and development of deep-seated coal rock gas. To reduce the cost of deep coal rock gas drilling fluid as the main research direction, to achieve the coal rock gas horizontal well speed and efficiency as the main goal, to carry out the deep coal rock gas horizontal well cost reduction research. Firstly, the main influencing factors of deep-seated coal rock collapse are analysed, and the enhancement of the sealing performance of drilling fluid on deep-seated coal rock is an important means to solve the problem of deep-seated coal rock collapse. The research on cost reduction of drilling fluid is based on the idea of ‘research low-cost multi-purpose treatment agents and reduce the amount of high-value treatment agents’. In terms of performance control, ‘highlighting key performance and moderately relaxing secondary performance’, on the premise of maintaining the performance of coal gas drilling fluid to meet the requirements of deep-seated coal gas sites, reduce or replace high-performance and high-value treatment agents through the use of low-cost multi-purpose treatment agents, so as to reduce the cost of drilling fluid and reduce the amount of high-value treatment agents.