Carbon dioxide acid fracturing method for low permeability heterogeneous carbonate gas reservoir

Abstract

The invention discloses a carbon dioxide acid fracturing method for a low permeability heterogeneous carbonate gas reservoir. The carbon dioxide acid fracturing method comprises the following steps that (1) CO2 tank trucks, a CO2 pump truck and fracturing trucks A are connected into a wellhead in series; (2) liquid tanks, acid tanks A and acid tanks B are directly connected with a low pressure manifold; (3) the low pressure manifold, a sand mixing truck, fracturing trucks B and a high pressure manifold are connected into the wellhead in series; (4) resistance reducing acid is subjected to pumpinjection with the displacement of 1.0-1.5m<3>/min; (5) CO2 is subjected to pump injection with the displacement of 1.5-3.0m<3>/min; (6) slickwater is subjected to pump injection with the displacement of 3.0-8.0m<3>/min; (7) the resistance reducing acid is subjected to pump injection with the displacement of 3.0-8.0m<3>/min; (8) steering acid is subjected to pump injection with the displacement of 2.0-6.0m<3>/min; (9) the steps (6)-(8) are repeated for 0-2 times, and the steps(6)-(7) are repeated for 1 time; and (10) the slickwater is subjected to pump injection. According to the carbon dioxide acid fracturing method, the acid fracturing effect can be improved, and the daily gas production quantity is increased.

Description

technical field [0001] The invention belongs to the technical field of oil and gas field reservoir transformation, and in particular relates to a carbon dioxide acid fracturing method for low-permeability heterogeneous carbonate rock gas reservoirs. Background technique [0002] With the continuous deepening of domestic exploration and development of oil and gas reservoirs, the physical properties of oil and gas reservoirs are getting worse and tighter. Especially for low-permeability heterogeneous carbonate gas reservoirs, acid fracturing (acid fracturing) is an effective measure for the commissioning and stimulation of oil and gas wells. It reacts chemically with the artificial (natural) fracture wall rock through the acid liquid to form groove-like or uneven high-permeability channels, thereby improving the seepage condition of the gas well and increasing the production of the gas well. [0003] In recent years, many domestic oil and gas fields have carried out research ...

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Problems solved by technology

[0004] There are four problems in the conventional acid fracturing method widely used at present: first, acid liquid is used for construction in the whole process. Filtration loss is out of control, resulting in extremely low efficiency of acid fluid fracture creation, making it difficult to form deep penetrating complex fracture networks, and unable to effectively communicate with oil and gas enriched areas; second, unilaterally increasing acid fluid viscosity to reduce fluid loss, and causing difficulties in flowback after fracturing , a large amount of high-viscosity acid fluid stays in the formation, causing reservoir damage; third, the acid-rock reaction rate is high, a large amount of acid fluid is consumed in the fracture near the wellbore and loses its activity, and the effective action distance of the acid fluid is limited so that it cannot act in the deep part of the fracture to form an effective seepage channel; Fourth, the amount of acid solution is large, which is not conducive to environmental protection

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