| Fracturing is the basic method to develop low pressure and low permeability reservoirs. It's critical to reduce the damage of fracturing fluid to reservoirs. Low filtration, low residue and fast flowing back are the premises of low reservoir damage. It is not just the gel broken residue, but also the effect that results from the filter liquor entering into formations that leads to reservoir damage, especially for low pressure and low permeability gas reservoirs. So the permeability of reservoirs is reduced greatly.Conventional water-base fracturing increases flowing back capacity and reduces the reservoir damage by means of thoroughly gel broken, however the more thoroughness of the gel broken, the more filter liquor volume entering into formations, which results in severe formation damage. Owing to the stress sensitivity of low permeability and temperature drop off of formations near fracture, reservoir permeability is decreased simultaneously when cold fluid invades into formations. So the satisfactory production increase can not be obtained easily.A new method was developed in this paper, which can solve the problem that fracturing fluid does harm to low pressure and to low permeability reservoirs, complete gel broken is not the only goal in this paper, a new kind of fracturing fluid was developed which has many excellent advantages such as self-generate heat and pressure increase automatically and flow back thoroughly, self-generate heat chemicals were introduced into the modified guar gel and at the same time the temperature of fracture fluid increases higher than ever, and a large quantity of inert gas gets out. So the flow back capacity of low-pressure reservoir was increased; gas scatters into the crossed-linked fracturing fluid and a type of fracturing fluid formed , which is similar to the foamed fracture fluid that results in decreasing the filtrate volume of fracturing fluid. Finally, Low damage in low permeability and low-pressure reservoir was achieved.Considering engineering demand, economic benefits and safety, NH4+ + NO2 -self-generation heat and building-up pressure system, TS-QA + TS-QB, was screened out. The chemical reaction environment is poor acid, in which the PH value is less than 5.the interaction velocity, gas volume and heat generation range can be realized by adjusting the concentrations and PH values of chemicals.That guar gel was modified chemically and cross-linking agent was screened out forms the modified guar gel and cross-linking agent system, which is SW-21+TS-CL. This system can well cross-link and cater for the PH value under weak acid circumstances. It integrates the pressure building-up by auto-generate gas, cross-linking and foaming. The cost is less than that of foamed fracture fluid, and it can obtain the same fracturing effect, which was achieved by employing foamed fracture fluid.Point to Laojunmiao M-reservoir, a new and low damage fracturing fluid was developed. It has lots of advantages, which includes auto-generate gas, pressure building-up, highsand-carrying capability, flow back quickly, little filtration, low reservoir damage and relative low cost. Also, the field application and facilities are relatively convenient and simple. Through the pilot test of 2 wells, three were achieved which is composed of optimizing the fluid and work process, exposing and resolving the problems and profit assessment. The field trails showed that this new fluid has priority in reforming low pressure and low permeability reservoirs.
|
PDF Full Text Request