A method of selective fracturing in layers

Abstract

The invention discloses an in-layer selective fracturing method. The in-layer selective fracturing method comprises the steps that (1), acid pretreatment is carried out; (2), a prepad fluid is injected with a low flow rate of 2-3m<3> / min; and a fracturing fluid is subjected to mixing injection by adopting quick water with the viscosity being 1-2mPa.s and low viscosity fracturing fluid with the viscosity being 10-20mPa.s; (3) the starting sand-liquid ratio is 2-3%, the stage amplification of sand-liquid ratio is set to 2-4%, and the maximum sand-liquid ratio is 20%; (4), replacing is carried out, liquid with volume being 1-2m<3> less than the volume of a shaft, and the displacement decreases gradually to 0; and (5), blowout after pressure is carried out, a well is closed for 1-2 hours untila fracture is closed, the blowout speed after the closure refers to the blowout speed of conventional fracturing and increases by 20-30%. The sand-adding scale, construction displacement fracturing fluid dosage, and sand liquid ratio of the in-layer selective fracturing method are lower than the current conventional fracturing requirements, the effective oil and gas reservoir can be fully reconstructed while reducing the construction cost, and wide application prospect and economic value are achieved.

Description

technical field [0001] The invention relates to the technical field of ultra-low permeability and tight sandstone oil and gas reservoir transformation, and furthermore, relates to a new selective fracturing method suitable for effective transformation in tight sandstone reservoir layers. Background technique [0002] At present, there are more and more ultra-low permeability and tight sandstone oil and gas reservoirs, such as the beach bar sand in Shengli and the Honghe Oilfield in Ordos. At present, vertical well layered fracturing and horizontal well staged fracturing technologies are generally adopted, and the scale of single layer and single stage fracturing sand addition is getting larger and larger. Although certain effects have been achieved, technically, there are still the following problems: [0003] (1) The oil and gas properties of ultra-low permeability and tight oil and gas reservoirs generally have a positive correlation with their physical properties. The be...

AI Technical Summary

Problems solved by technology

For ultra-low permeability and tight oil and gas reservoirs, the existing fracturing concept is to carry out large-scale fracturing, that is, large construction displacement and construction scale, but the fracture height and fracture length of large-scale fracturing are relatively large, making All oil-gas-rich and oil-gas-poor areas have been crushed at one time, and the area of ​​fractures that produce oil and gas may only account for a small proportion of the total area, or even only 10% or less of the effective reservoir, resulting in fracturing fluid, support Great waste of agent and equipment power

[0004] (2) The compatibility and anti-swelling properties of the fracturing fluid formula are optimized or optimized only by considering the mineral composition and sensitivity of the reservoir. Mudstone interbedded, the above fracturing fluid formula may not be applicable

On the one hand, a single fracturing fluid formulation can easily cause mudstone hydration and large-area expansion and migration of clay due to large-scale fracturing that simultaneously depresses both the reservoir and the mudstone interlayer, resulting in the formation of ineffective fractures and even swollen mud cakes. The material will flow to the well-flowing sandstone or areas with high sandstone content, causing great damage to the effective fracture conductivity, and it is difficult to alleviate or eliminate

[0005] (3) In areas with high shale content, rock plasticity is enhanced, and fracture initiation and extension are difficult, which will also cause passive situations such as early sand plugging

However, there is no reference to how to achieve sufficient fracturing in a reservoir