Application of Drilling Fluid Technology in Drilling a Long Horizontal Section Well in Block Fengxi in Qinghai

To obtain high production rate with less oil and gas wells, The Qinghai oilfield decided to drill five long open hole horizontal wells in the Fengxi structure which is located in the Dafengshan area in Qaidam Basin. Water-based and oil-based drilling fluids were to be used to drill these wells, and the results be compared to improve and perfect the technical prototype for future drilling and completion of long open hole and long horizontal section horizontal wells in the same area. This paper summarizes the field engineering of a high-quality compound saltwater drilling fluid on the well Fengxi IH1-5 and analyses are briefly conducted on the application, control of the engineering parameters, rheology and sand carrying capacity of the drilling fluid. The well Fengxi IH1-5, which is 5,487 m in depth, has a length of horizontal section of 2,541 m, the longest horizontal section in the Qinghai oilfield. This well has broken several records in this oilfield, such as penetrating the highest percentage of pay zones (100%), the longest footage (1,566 m) drilled in a single bit run, the longest horizontal section (1,000 m) in which short trips were performed, as well as the first application of casing floatation technology in casing running etc. The success of the drilling operation has milestone significance in applying the ultralong horizontal section well drilling technology in the Qinghai oilfield. Compared with the drilling operation of the offset wells drilled with oil-based drilling fluids, the use of this high-quality compound saltwater drilling fluid has gained better results in drilling than the oil-based drilling fluids previously used in other wells. The success gained in applying the water-based drilling fluid has provided a good guidance for optimizing the properties of water-based drilling fluids for horizontal wells with long open hole and long horizontal sections.