Low Oil-Water Ratio Technology in Water-In-Oil Drilling Fluids for Cost Reduce of Unconventional Oil and Gas Drilling Fluids

Abstract

In China’s unconventional oil drilling, horizontal wells are one of the main forms of drilling, water-in-oil drilling fluid have been widely used due to their stable performance and excellent lubricating properties. To reduce the high cost of water-in-oil drilling fluids at the drilling site, further reduce the pressure of cuttings processing, and meet the requirements of environmental protection, an oil-based drilling fluid system with a low oil-water ratio was developed. Based on the research of key emulsifiers and the introduction of nanomaterials, it helps the drilling fluid system maintain the performance of the drilling fluid while increasing the water-phase ratio, and further enhances the fluid loss performance of the drilling fluid. The developed low oil-water ratio oil-based drilling fluid has been applied in the horizontal section of Jiaoye 5-3HF and Jiaoye 21-S2HF, two wells in the Fuling shale gas block in China, and successfully drilled to the designed well depth. The Marsh funnel viscosity of the drilling fluid is controlled from 63s to 78s, the plastic viscosity is lower than 40 mPa·s, the dynamic shear force is maintained at 3.5–7 pa, the high temperature and high pressure water loss is controlled below 2.6 ml, and the demulsification voltage is stable above 600v; the properties of the drilling fluid Excellent, meeting the requirements of on-site drilling construction. Compared with the conventional oil-water ratio system, the oil-based drilling fluid system with low oil-water ratio can greatly reduce the oil content, which can meet the requirements of on-site drilling and save the cost of oil-based drilling fluid to a large extent. It can reduce the pressure of environmental protection to a certain extent.