Case Study of Fracturing Fluid Optimization for MHF in a Low-Permeability Gas-Field in China

Abstract

Abstract This paper describes a fracturing fluid optimization design of massive hydraulic fracturing for low permeability gas field. Computer simulations and fluid design methodology are proposed for fracturing fluid optimization design, which enables fracturing fluid to balance the contradictory requirement between conductivity and fracturing fluid breaking for viscosity and obtain maximum conductivity supporting the fracture belt. Three wells have been successfully stimulated using the fluid system designed with the method in Chuanzhongbajiaochang. The article introduces two typical cases. The massive hydraulic fracturing was implemented with 244 and 352 metric tons of proppant pumped into the wells respectively. Initial gas rate for both wells was 17×104m3/d. The scale of the jobs broke the records in Chinese hydraulic fracturing history. This work sets a start of massive hydraulic fracturing for low permeability gas fields in China. Introduction China has large number of low-permeability sandstone gas field and the Western Development policy and gas conveyance from west to east require economical and effective development of these low-permeability gas fields. In North America, tight gas reservoir adopts massive hydraulic fracturing method and achieves high yield and benefits. But in China, most gas fields had hydraulic fracturing scale below 30m3 (not up to 60 tons). Initial gas rate ranged from 0.5 to 2×104m3/d, which seriously hindered development and increase of low-permeability gas fields and could not form economical and effective development. Since massive hydraulic fracturing construction has massive scale, longer operation and puts special requirement for fracturing fluid and equipment, especially in recent years many fracturing equipment has been imported directly from abroad, domestic fracturing fluid has become key technology for successful hydraulic fracturing when it can compete with that big foreign companies. To meet the requirements for fracturing fluid in terms of construction and protection reservoir as put up by massive hydraulic fracturing fluids and solve the contradiction between requirement of construction scale and fast breaking discharge for viscosity, Fracturing and Acidizing Technical Service Center proposes fracturing fluid optimization design for massive hydraulic fracturing in low-permeability gas fields. Relatively cheap domestic materials are used, which meets the requirements of the gas reservoir characters and process and reduces at the maximum the impact of fracturing fluid over the reservoir and conductivity of the support fracture. The typical case for successful application of the technology is the massive hydraulic fracturing construction for three wells at Chuan Zhong Ba Jiao Chang. The technology is proved to be applicable, which adapts to the specialized service of foreign companies but more important, puts up new concept for fracturing fluid of massive hydraulic fracturing for more low-permeability gas fields and contributes to the development of low-permeability gas fields in the west. Optimization Design Technology for Fracturing Fluids of Massive Hydraulic Fracturing Operation Concept and technical idea on fracturing fluid optimization design. Fracturing fluid optimization design technology aims to realize massive scale at low damage and cost, proposes different fracturing formulations for different fracturing processes of the same well based on the impact of fracturing fluids' property by temperature profile, shear rate profile and polymer condensation, and basically attains constant changing operation of the fracturing fluids. The technology includes additional breaking agent, reducing gelling agent and cross-linker, changing cross-linker composition. Refer to following flowchart for fracturing fluid optimization design technology. Concept and technical idea on fracturing fluid optimization design. Fracturing fluid optimization design technology aims to realize massive scale at low damage and cost, proposes different fracturing formulations for different fracturing processes of the same well based on the impact of fracturing fluids' property by temperature profile, shear rate profile and polymer condensation, and basically attains constant changing operation of the fracturing fluids. The technology includes additional breaking agent, reducing gelling agent and cross-linker, changing cross-linker composition. Refer to following flowchart for fracturing fluid optimization design technology.