Stepless variable-viscosity on-site hydraulic fracturing method free of preparation of slick water

Abstract

The invention provides a stepless variable-viscosity on-site hydraulic fracturing method free of preparation of slick water. The method comprises the steps that construction design of all stages of fracturing is conducted according to limiting conditions of a fracturing construction site; according to the formation water mineralization degree-drag reducer concentration-drag reduction rate relation chart and the formation water quality of the fracturing transformation interval, the drag reducer concentration range is determined; according to the flow velocity-drag reducer concentration-drag reduction rate relation chart, the displacement of the prepad fluid construction stage and the displacement of the displacing fluid construction stage under the condition that the wellhead pressure is certain are determined; according to the flow velocity-drag reducer concentration-drag reduction rate relation chart, the drag reducer concentration-viscosity-viscoelasticity relation chart and the construction displacement-viscoelasticity-sand ratio relation chart, the displacement, the sand ratio, the viscosity of the fracturing fluid and / or the drag reducer concentration in the sand-carrying fluid construction stage under the condition of certain wellhead pressure are determined; and according to the determined result, prepad fluid and sand-carrying fluid are alternately injected into all the fractured interval sections for multiple times, and displacement fluid is injected into the fractured interval sections so that the sand-carrying fluid in the shaft can be pressed into the fractures.

Description

technical field [0001] The invention relates to an on-site hydraulic fracturing method with stepless viscosity change without mixing slick water, in particular to a method for fracturing reservoirs with stepless viscosity change without mixing slick water, and belongs to the technical field of oil and gas field exploration and development. Background technique [0002] Hydraulic fracturing technology plays an important role in the stimulation of unconventional oil and gas reservoirs. According to the geological characteristics of unconventional oil and gas reservoirs in my country, most of the fracturing fluids used in fracturing sites are slick water systems, accounting for 70%-80%. Slick water is generally composed of additives such as water, sand, drag reducer, bactericide, clay stabilizer and drainage aid, which can reduce frictional pressure by 70%-80% compared with clean water, and has strong anti-swelling performance. And its viscosity is low, generally below 10mPa·s...

AI Technical Summary

Problems solved by technology

Although this method can achieve the purpose of multi-stage fracture creation and volume fracturing, it does not consider the influence of the viscoelastic properties of slick water on sand-carrying performance. To increase the sand ratio of the slick water sand-carrying fluid by increasing the displacement does not take into account the stepless adjustment of the viscoelasticity of the slick water itself, so it has no practical significance

Although the above-mentioned existing technologies can solve the problem of suspended sand, firstly, neither of them can guarantee the sand-spraying state in the fracture (sand plugging is easy to form), and secondly, the fracturing site may not be able to guarantee high displacement and fluid volume, especially It is offshore construction, resulting in limited scope of application

[0004] At present, the on-site slickwater fracturing operation has problems such as complex process, long construction time, and low economic benefits, and the existing slickwater system cannot realize stepless adjustment of viscosity, and it is usually necessary to replace high-viscosity guar gum in the sand-carrying fluid stage Fracturing fluid system to achieve the expected fracturing effect

Images