CN103194202B - Adsorptive acid liquor retarding admixture and preparation method thereof - Google Patents

Abstract

The invention relates to an adsorption type acid liquid retarding admixture used in the acidification of oil and gas wells and a preparation method thereof. Its technical solution: the molar percentage of the monomers used in the acid retarder admixture is: octadecyl dimethyl allyl ammonium chloride code name BAZ monomer is 4.2 ~ 4.7%, allyl polyethylene glycol code name The APEG monomer is 1.9-2.3%, the acrylamide code AM monomer is 93-93.5%, and the initiator is azobisisobutylamidine hydrochloride, accounting for 0.4-0.5% of the total monomer mass. Add BAZ, APEG and AM into the reaction vessel, then add water to form a solution with a concentration of 10% monomer mass, add an initiator, mix well, and react at 50-55°C for 6-7 hours to obtain the acid Liquid retarding admixture. The preparation method of the invention is simple and feasible, the reaction conditions are mild, the product has good thermal stability, can be adsorbed on the wall surface of formation fractures, delays the reaction speed of acid liquid and the wall surface of fractures, achieves the effect of deep acidification, and is used for preparing acidification liquid.

Description

A kind of adsorption type acid retarding admixture and preparation method thereof

technical field

The invention relates to an adsorption-type acid retarding admixture used in the acidizing operation of the petroleum and natural gas industry and a preparation method thereof.

Background technique

Acidizing is one of the important production stimulation measures for oil and gas reservoirs. It is a production stimulation measure that uses acid liquid to remove pollution near the bottom of production wells and injection wells, restore formation permeability or dissolve formation rock cement to increase formation permeability. Its purpose is to use acid to relieve the damage caused to the formation near the wellbore during the process of drilling, well completion, well workover and enhanced injection, and dredge the fluid seepage channel, so as to restore and increase the productivity of oil and gas wells. At present, based on the scale of acid-etched fractures, the acid fracturing technology can be divided into two categories: ordinary acid fracturing and deep acid fracturing.

Ordinary acid fracturing is mainly to remove the pollution near the wellbore or form small-scale acid-etched fractures to improve the conductivity of the formation near the wellbore. However, ordinary acid fracturing has severe acid fluid loss, fast acid-rock reaction speed, short effective acid etching distance, and even pollutes serious reservoirs with well-developed natural fractures.

Deep acid fracturing is aimed at the rapid reaction between ordinary acid fracturing and reservoirs, and the effective action distance of acid fluid is short, resulting in the consumption of most of the acid fluid in formations near the wellbore, while the deep part is not fully acidified, which makes the effect of stimulation measures worse The retarded acid system with different characteristics has been developed, mainly including gelling acid, emulsifying acid, chemical retarding acid, foaming acid, and viscous acid.

Gelling acid is a polymer solution with high viscosity. The main technical feature of gelling acid is that adding a gelling agent to the acidizing solution makes the acid solution system a lyophilic sol and reduces the diffusion rate of H+, thereby reducing the reaction rate of acid rock, increasing the penetration distance of active acid, and achieving deep acidification Effect. Gelled acid has the advantages of saving the amount of corrosion inhibitor, reducing pumping friction, and reducing formation damage, but it is very sensitive to shear, and it is difficult to break the gel in residual acid, which is easy to cause secondary pollution to the reservoir.

Emulsified acid usually refers to the oil-in-acid emulsion formed by mixing two immiscible liquids, oil and acid, in an appropriate proportion and under the action of an emulsifier. The mechanism of action is to use the high viscosity of the emulsified acid and the hindering effect of the external phase oil to delay the contact between the acid liquid and the fracture wall and delay the acid-rock reaction rate. Its advantages are small filtration loss, good retarding performance, and can penetrate deep into the formation; the disadvantage is that the construction friction is relatively high, which is higher than that of ordinary acid, resulting in high acid fracturing construction pressure and low displacement.

Chemical slow acid refers to the acid system formed by adding surfactants to the acid solution or adding surfactants that make the CO2 generated by the acid rock reaction form a stable foam. Its mechanism of action is that the surfactant is adsorbed on the fracture wall of the formation to form a protective film to delay the reaction rate of acid rock; its disadvantage is poor control of filtration loss, and it is mainly suitable for low-temperature dolomite formations where the reaction rate of acid rock is controlled by the surface. The combination of alternate injection techniques can be applied to mesophilic dolomite reservoirs.

Foam acid uses aerated or gasified acid liquid instead of conventional acid liquid to reduce the reaction rate of acid rock and achieve deep penetration. Foam acid is composed of acid liquid, gas, foaming agent, foam stabilizer, water-soluble polymer, etc. It has the advantages of low liquid content, high apparent viscosity, and small fluid loss, which can effectively slow down the reaction rate of acid rock and quickly flow back. However, under high temperature conditions, the stability of foam acid decreases, and the fluid loss of acid liquid increase, thus affecting the retarded acidification effect.

Viscosity acid, also known as fluid loss control acid, refers to adding a synthetic compound to the acid solution, which can form a cross-linked gelling agent in the formation to increase the viscosity, and can automatically break the gel and reduce the viscosity after the acid solution is consumed as residual acid acid system.

Viscosified acid has good fluid loss control performance, stable viscosity-temperature performance and low residual acid viscosity, but it is more sensitive to hydrogen sulfide.

Contents of the invention

The purpose of the present invention is: in the acidizing operation, the conventionally used acid liquid hydrochloric acid and earth acid are both strong acids, and the formation reacts with them quickly, and generally can only eliminate the damage of the permeability around the well, in order to achieve acidification of deep formations and improve the production capacity of oil and gas fields , especially provide an adsorption type acid retarding admixture and a preparation method thereof.

In order to achieve the above object, the present invention adopts the following technical solutions: an adsorption type acid retarding admixture, characterized in that: the acid retarding admixture is made of octadecyl dimethyl allyl ammonium chloride code BAZ, allyl polyethylene glycol code name APEG, and acrylamide code name AM three monomers are polymerized; the molar percentage of the monomers used is: BAZ monomer is 4.2-4.7%; APEG monomer is 1.9-2.3%. The relative molecular mass of the APEG monomer used is 1000g/mol; the AM monomer is 93-93.5%; the initiator is azobisisobutylamidine hydrochloride, and the addition amount is 0.4-0.5% of the total mass of the monomer. Its structural formula of this acid retarder admixture is as follows:

Among them, X=4.2～4.7%, Y=1.9～2.3%, n=20～25.

A kind of preparation method of absorption type acid liquid retarding admixture, its step is, first in the silk mouth reagent bottle that volume is 100mL, add the octadecyl dimethyl allyl ammonium chloride BAZ of 0.002mol and 0.001mol Allyl polyethylene glycol APEG and 0.04mol of acrylamide AM; then add 41.3g of deionized water to the above solution to form a solution with a monomer mass percentage concentration of 10%, stir and dissolve and then add the initiator couple Azodiisobutylamidine hydrochloride 0.018g; finally, after mixing the above solution evenly, react at a temperature of 50-55°C for 6-7h to obtain a colloidal product, which is washed 3-5 times with absolute ethanol until it appears Precipitation, after drying in an oven at a temperature of 50°C for 24 hours, the acid retarder admixture is obtained.

Compared with the existing acid retarding admixture, the present invention has the following beneficial effects: (1) The preparation method of the present invention is simple and feasible, and the reaction conditions are mild. (2) After the product is added to the acid system, it has a good retarding effect in sandstone and carbonate, and can acidify deep formations, and the viscosity of the acid system does not change significantly, which is conducive to the removal of residual acid Flowback. (3) The product prepared by this method has good thermal stability, strong temperature resistance, and good compatibility with other additives in the acid system.

Detailed ways

Example 1 A preparation method of an adsorption-type acid retarding admixture

First, add 0.747g or 0.002mol of octadecyldimethylallyl ammonium chloride BAZ and 1g or 0.001mol of allyl polyethylene glycol APEG and 2.84g of 0.04mol of acrylamide AM; then add 41.3g of deionized water to the above solution to form a solution with a monomer mass percentage concentration of 10%, stir and dissolve and add 0.018g of initiator azobisisobutylamidine hydrochloride Finally, after mixing the above solutions evenly, react at a temperature of 50°C for 6 hours to obtain a colloidal product, wash with absolute ethanol for 3 times until precipitation occurs, and dry in an oven at a temperature of 50°C for 24 hours to obtain this product Acid retarding admixture.

Example 2 A preparation method of an adsorption-type acid retarding admixture

First add 0.672g (0.0018mol) of octadecyldimethylallyl ammonium chloride BAZ and 1g (0.001mol) of allyl polyethylene glycol APEG and 2.84g (0.001mol) to a silk-top reagent bottle with a volume of 100mL. 0.04mol of acrylamide AM; then add 40.6g of deionized water to the above solution to form a solution with a monomer mass percentage concentration of 10%, stir and dissolve and add 0.018g of initiator azobisisobutylamidine hydrochloride Finally, after mixing the above solutions evenly, react at a temperature of 50°C for 6 hours to obtain a colloidal product, wash with absolute ethanol for 3 times until precipitation occurs, and dry in an oven at a temperature of 50°C for 24 hours to obtain this product Acid retarding admixture.

Example 3 A preparation method of an adsorption-type acid retarding admixture

First add 0.672g or 0.0018mol of octadecyldimethylallyl ammonium chloride BAZ and 0.8g or 0.0008mol of allyl polyethylene glycol APEG and 2.84g That is, 0.04mol of acrylamide AM; then add 38g of deionized water to the above solution to form a solution with a monomer mass percentage concentration of 10%, stir and dissolve and add 0.017g of initiator azobisisobutylamidine hydrochloride Finally, after mixing the above solutions evenly, react at a temperature of 50°C for 6 hours to obtain a colloidal product, wash with absolute ethanol for 3 times until precipitation occurs, and dry in an oven at a temperature of 50°C for 24 hours to obtain this product Acid retarding admixture.

Example 4 The retarding effect of an adsorption-type acid retarding admixture in sandstone

In order to evaluate the retarding performance of the acid retarding admixture in sandstone, refer to the static weight loss method in SY/T5886-93 sandstone retarding acid performance evaluation method. The process is as follows: first, put the acid solution system of earth acid and retarding admixture into two 100mL silk-top reagent bottles, and then put it into a constant temperature water bath at 80°C. Add the corresponding sandstone cuttings. The dissolution rate was measured sequentially when the reaction time was 30 or 45 or 60 or 90 minutes. Then wash, filter, dry, weigh, and calculate the core dissolution rate under different conditions. Finally, it is proved that the retarding admixture acid system has better acid retarding effect than conventional soil acid.

Example 5 The retarding effect of an adsorption-type acid retarding admixture in carbonate rocks

In order to evaluate the retarding performance of the acid retarding admixture in carbonate rocks, two cuboid carbonate rock samples with a length of 2mm, a width of 1mm and a height of 1mm were first prepared, and the surface area was calculated to an accuracy of 0.01m2 , put into the desiccator to dry for 30min. Then measure 3mL of hydrochloric acid and hydrochloric acid with retarding admixture (20% concentration of hydrochloric acid by mass) for each rock sample according to the surface area of each square centimeter, and put them in the reaction bottle, and move the reaction bottle into a constant temperature water bath at 80°C to wait for the acid solution. After the temperature is constant, add rock samples, measure the dissolution rate with a reaction time of 30 or 45 or 60 or 90 minutes in sequence, and finally wash, filter, dry, and weigh to calculate the dissolution rate of rocks under different conditions. It is found by experimental results that after adding the acid retarding admixture prepared by the invention, the acid has a better retarding effect.

Claims (1)

1. the slow admixture of adsorptive type acid solution, is characterized in that: the slow admixture of this acid solution is to be formed by solution property code name BAZ, allyl polyglycol code name APEG, tri-kinds of monomer polymerizations of acrylamide code name AM; The molar percentage of monomer used is: BAZ monomer is 4.2～4.7%; APEG monomer is 1.9～2.3%, and the relative molecular mass of APEG monomer used is 1000g/mol; AM monomer is 93～93.5%; Initiator is azo-bis-isobutyrate hydrochloride, and add-on is 0.4～0.5% of monomer total mass; Its preparation method is: the acrylamide AM that adds the solution property BAZ of 0.002mol and the allyl polyglycol APEG of 0.001mol and 0.04mol in the silk opening reagent bottle that is first 100mL at volume; Then being made into monomer mass percentage concentration to the deionized water that adds 41.3g in above-mentioned solution is 10% solution, adds initiator azo-bis-isobutyrate hydrochloride 0.018g after stirring and dissolving; After finally above-mentioned solution being mixed, being to react 6-7h at 50-55 DEG C in temperature, obtaining colloid product, use absolute ethanol washing 3-5 time, until there is precipitation, is to dry after 24h in 50 DEG C of baking ovens in temperature, makes the slow admixture of this acid solution.