Bio-enzyme gel breaker and technique for water-based guargum fracturing gel breaking with the same

Abstract

The invention relates to bio-enzyme gel breaker, in particular to formula and technique for gel breaking of water-based guargum fracturing fluid by using the bio-enzyme gel breaker. The bio-enzyme gel breaker contains the following components in percentage by weight: 10-50% of beta- mannose, 0-20% of cellulose, 0-10% of pectinase, 0-15% of glucanase, 0-10% of xanthase, 3-10% of (NH4)2SO4, 2-5% of NaCl, 1.5-5% of ZnCL2 and 0-60% of persulfate. The fracturing fluid gel breaking technique comprises the following steps: dissolving the bio-enzyme gel breaker in borax crosslinked fluid; mixing and blending the crosslinked fluid and the guargum base fluid, crosslinking, forming jelly, and then mixing with proppant, pressing the mixture into the oil-water well until the mixture enters the fractured crack. In this way, the fracturing process is finished. The bio-enzyme gel breaker degrades the macromolecular guargum in the stratum fracturing fluid into small micromolecular sugar, and when the jelly breaks up, the proppant is left underground, the fracturing gel breaking fluid flows back, and in this way, the construction can be completed. The bio-enzyme gel breaker has good gel breaking performance, the construction process is reasonable, the viscosity of the fracturing fluid can not decrease too early, the gel of the fracturing fluid can be broken evenly and thoroughly with little residue and small harm to the stratum, and the operation is simple and convenient.

Description

technical field [0001] The invention relates to the formulation of a biological enzyme gel breaker for water-based guar gum fracturing fluid in oilfield development and a process for using biological enzymes to break gel, specifically, using the developed biological enzyme gel breaker and the use of biological enzymes to break the gel. A gel breaking process for water-based guar gum fracturing fluid. Background technique [0002] In order to increase the production of single well and improve the ultimate recovery rate of oilfield, oilfields often use fracturing to reform the production wells. The quality of the fracturing effect directly affects the production stimulation effect after the fracturing measures. At present, fracturing is one of the important measures to increase production in oilfields (especially low-permeability-ultra-low-permeability oilfields). The displacement pressure gradient from the reservoir to the bottom of the well is the key to increasing product...

AI Technical Summary

Problems solved by technology

99808877.3 and 200610106884.4 describe a new mannanase, which mentions that the enzyme can be used in water-based guar gum fracturing fluid, but there is no specific method of use, because the fracturing site environment is complex and the conditions are harsh (pH It must be alkaline or strongly alkaline), and has strict requirements on biological enzymes. Various additives (such as fungicides) in the fracturing fluid have a greater impact on the activity of biological enzymes, which is determined by the performance requirements of the fracturing fluid during the fracturing process. The biological enzyme must play a role in the whole process; especially in the later stage of fracturing, the biological enzyme degrades the guar gum residue in the fracturing fluid and turns it into a clear liquid, reducing the damage to the formation

[0006] Articles about bio-enzyme breaking, mainly the article "Indoor evaluation of bio-enzyme breaking agent and its application in oilfield fracturing", in this article The gel breaking enzyme described is a single enzyme, and there is no control analysis on the residue content after gel breaking

The purpose of using biological enzymes to break the gel is mainly to reduce the residue. The smaller the residue content, the better the gel breaking effect, the less damage to the formation, and it will not block the formation, which is more conducive to the outflow of crude oil from the formation; another article It is "the research and application of a new biological enzyme gel breaker", in which there is no application data, no effect analysis, no specific dosage, and no feasibility and economic comparison

Judging from the current research progress and field application, although there is a single biological enzyme (mannanase or cellulase) that can be used in water-based guar gum fracturing fluid, and it has been applied in oil well fracturing production. , but its cost is several times or even ten times that of persulfate breakers, and the biological enzymes used may not be able to reduce residues

At the same time, many problems occurred in the process of fracturing and breaking rubber. In addition to the unstable performance of the enzyme itself under alkaline conditions and harsh construction environments, another important reason is that guar gum is a natural macromolecular substance. It also contains some other polysaccharide impurities, such as cellulose, hemicellulose, various gums, etc. In addition, guar gum is connected by β-1, 4 glycosidic bonds and α-1, 6 glycosidic bonds. Enzymes generally only have special effects on one of the glycosidic bonds

Therefore, the use of a single biological enzyme for fracturing fluid gel breaking may result in incomplete or incomplete gel breaking due to the quality and source of guar gum, which shows that the gel breaking is not stable enough and the residue content is high

In addition, the bio-enzyme construction process has a great impact on the bio-enzyme activity and the gel-breaking process. The fracturing technology currently used does not target the characteristics of bio-enzymes: if bio-enzymes are added to the base fluid, the bio-enzymes will work prematurely , degrade the macromolecules of guar gum, resulting in a decrease in the viscoelasticity of the fracturing fluid. If there is a failure during the construction process, the residence time is too long, the base fluid is completely degraded, and cannot be cross-linked with the cross-linking agent to form a gel, which makes the fracturing operation impossible ; or the unreasonable preservation and use of biological enzymes lead to the loss of biological enzyme activity before injection into the formation, resulting in the failure of the biological enzyme to break the gel, resulting in the non-flowback of the fracturing fluid, and the failure of the operation; or the biological enzyme is added to the cross-linked jelly , due to the current technology, it is impossible to fully mix the biological enzyme with the cross-linked glue, the distribution of the biological enzyme gel breaker in the fracturing fluid is uneven, and the partial gel breaking of the fracturing fluid in the formation is not complete, resulting in insufficient gel breaking Complete, there is a dead angle, which affects the fracturing effect

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