Study on Weighted Slick Water Fracturing Fluid for Deep Buried Oil and Gas

In fracturing the ultradeep gas reservoirs in the piedmont structure in Kuche, Tarim Basin, 75% of the wells were operated at pump pressures above 100 MPa, the highest pump pressure being 136 MPa. The development of the gas reservoirs has long been limited by the fracturing operation because of the high pump pressures. Statistic data showed that when fracturing ultradeep wells, an increase in the density of the fracturing fluid did not result in the designed pump pressure decrease. Based on theoretical analysis and problems encountered in fracturing with high density fracturing fluids, a weighted slick water fracturing fluid was developed with several agents selected such as a weighting agent, a salt resistant friction reducer and a cleanup additive. In developing the slick water fracturing fluid, experiences of successfully using slick water in shale gas development were borrowed, and the advantages of weighted fracturing fluids were taken. The slick water fracturing fluid has a density of 1.35 g/cm³ and is resistant to the contamination by 35×10⁴ mg/L of CaCl₂. With this slick water, the operation pressure can be effectively reduced and operation risks minimized. Similar to conventional guar gum fracturing fluids, this slick water can reduce friction by 62%. The slick water has good high temperature stability and cleanup ability. It is resistant to shearing. Cores tested with this slick water had permeability impairment of only 11.2%. The development of the slick water fracturing fluid has provided a technical support to the stimulation of ultra-high pressure and ultradeep reservoirs.