阅读说明：本技术 一种无黏土相合成基钻井液及其制备方法 (Clay-free phase synthetic base drilling fluid and preparation method thereof ) 是由 王磊磊 陈庭贵 郭剑梅 闫晓婷 张现斌 张坤 马红 郭立华 高宁 张鹏 赵颖 于 2019-11-15 设计创作，主要内容包括：本发明公开了一种无黏土相合成基钻井液,包括以质量分数计的60％～95％的合成基础油和5％～40％盐水,二者质量分数总计为100％；以及以合成基础油和盐水总重量计的2％～6％的乳化剂、0.5％～1％的流型调节剂、2％～3％的氧化钙、2％～3％的降滤失剂和50％～500％的惰性加重材料；该无黏土相合成基钻井液通过将合成基础油、盐水、乳化剂、氧化钙、降滤失剂和惰性加重材料按照一定比例混合复配而成,除实现在钻井液体系中去除了有机土这一成分外,还具有增大钻井液的固相容限,提升高温和高密度条件下的流动性的特点,能够进一步获得更好的保护储层。(The invention discloses a clay-free phase synthetic base drilling fluid, which comprises 60-95% of synthetic base oil and 5-40% of brine by mass, wherein the mass percentages of the synthetic base oil and the brine are 100%; 2 to 6 percent of emulsifier, 0.5 to 1 percent of flow pattern regulator, 2 to 3 percent of calcium oxide, 2 to 3 percent of filtrate reducer and 50 to 500 percent of inert weighting material based on the total weight of the synthetic base oil and the salt water; the clay-free phase synthetic base drilling fluid is prepared by mixing and compounding synthetic base oil, saline water, an emulsifier, calcium oxide, a filtrate reducer and an inert weighting material according to a certain proportion, and has the characteristics of increasing the solid phase tolerance of the drilling fluid and improving the mobility under the conditions of high temperature and high density besides removing the component of organic soil in a drilling fluid system, so that a better reservoir protection layer can be further obtained.)

1. The clay-free phase synthetic base drilling fluid is characterized by comprising 60-95% of synthetic base oil and 5-40% of brine in mass percentage, wherein the total mass percentage of the synthetic base oil and the brine is 100%; 2 to 6 percent of emulsifier, 0.5 to 1 percent of flow pattern regulator, 2 to 3 percent of calcium oxide, 2 to 3 percent of filtrate reducer and 50 to 500 percent of inert weighting material based on the total weight of the synthetic base oil and the salt water; wherein the content of the first and second substances,

the saline water is a sodium chloride solution, a calcium chloride solution, a potassium chloride solution, a sodium formate solution, a potassium formate solution or a cesium formate solution with the mass fraction of 20-25%;

the emulsifier is compounded by alkyl glucose amide, anionic surfactant and nonpolar solvent; the alkylglucamide is prepared from 27-50 parts by weight of glucose methylamine, 29-43 parts by weight of monobasic fatty acid or monobasic fatty acid ester, 9-27 parts by weight of polar solvent and 0.12-0.16 part by weight of sodium alkoxide, and the molecular structural formula of the alkylglucamide is shown as the following formula:

wherein n is any integer of 5-17, and n is an odd number; the polar solvent is C₁～C₄The small molecule monohydric or dihydric alcohol of (a); the anionic surfactant is 1-3 parts by weight of sulfate salt type anionic surfactant; 7-9 parts by weight of a non-polar solvent, and the synthetic base oil has a kinematic viscosity of 2-6 mm at 40 DEG C²A synthetic base oil per second;

the flow pattern regulator is an alkylglucamide with two glucose chain segments, which is generated by the reaction of dibasic fatty acid with a carbon chain length of 6-18 and methyl ester thereof with glucose methylamine, or an alkylglucamide with a plurality of glucose chain segments, which is generated by the reaction of polybasic fatty acid with a carbon chain length of 10-18 and methyl ester thereof with glucose methylamine; the molar ratio of the amino group of the glucose methylamine to the carboxyl group of the fatty acid is 1: 1.2-1.6; the molar ratio of the amino group of the glucose methylamine to the ester group of the fatty acid methyl ester is 1: 1.2-1.6.

2. The clay-free phase synthetic base drilling fluid of claim 1, wherein the synthetic base oil is a gas oil synthetic base oil, a poly α -olefin synthetic base oil, a synthetic ester synthetic base oil, an internal olefin synthetic base oil, or a polyether synthetic base oil.

3. The clay-free phase synthetic based drilling fluid according to claim 1, wherein the fluid loss additive is at least one of lignite resin, pitch oxide.

4. The clay-free phase synthetic-based drilling fluid of claim 1, wherein the inert weighting material is at least one of limestone, barite, hematite.

5. The clay-free phase synthetic based drilling fluid according to claim 1, wherein the sulfate ester type anionic surfactant is fatty alcohol sulfate, fatty alcohol polyoxyethylene ether sulfate, glycerol fatty acid ester sulfate or sulfated sodium ricinoleate.

6. The clay-free phase synthetic based drilling fluid of claim 1, wherein the polar solvent is at least one of ethanol, propanol, butanol, propylene glycol.

7. The clay-free phase synthetic based drilling fluid of claim 1, wherein the monobasic fatty acid or fatty acid ester is caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid or stearic acid, methyl caproate, methyl caprylate, methyl caprate, methyl laurate, methyl myristate, methyl palmitate or methyl stearate; the dibasic fatty acid is adipic acid, oxalic acid, dodecanedioic acid, hexadecanedioic acid or octadecanedioic acid; the polybasic fatty acid is a deca-or octadeca-tribasic fatty acid.

8. The method for preparing the clay-free phase synthetic-based drilling fluid according to claim 1, wherein the method comprises the following steps:

s1, adding glucose methylamine and dibasic fatty acid, glucose methylamine and dibasic fatty acid methyl ester, glucose methylamine and polybasic fatty acid or glucose methylamine and polybasic fatty acid methyl ester into a polar solvent, mixing and stirring uniformly, adding a sodium alkoxide catalyst, heating to 130-140 ℃, carrying out reflux reaction for 4-5 hours, then carrying out rotary evaporation to remove the polar solvent in the mixed solution, cooling to obtain a waxy solid, and drying and crushing to obtain a flow pattern regulator product; wherein the dosage of the polar solvent is 1.9-2.8 times of the total weight of the glucose methylamine and the fatty acid, or 1.9-2.8 times of the total weight of the glucose methylamine and the fatty acid methyl ester; the adding amount of the sodium alkoxide catalyst is 0.1 to 0.21 percent of the total weight of the glucose methylamine and the dibasic or polybasic fatty acid, or 0.1 to 0.21 percent of the total weight of the glucose methylamine and the dibasic or polybasic fatty acid methyl ester;

s2, adding glucose methylamine and monobasic fatty acid or glucose methylamine and monobasic fatty acid ester into a polar solvent, uniformly mixing, adding a sodium alkoxide catalyst, heating to 120-130 ℃, performing reflux reaction for 2-5 hours to generate an alkyl glucosamide solution, adding a non-polar solvent and an anionic surfactant while hot, and uniformly stirring to obtain an emulsifier product; wherein the feeding molar ratio of the glucose methylamine to the monobasic fatty acid is 1: 0.8-1.22, and the feeding molar ratio of the glucose methylamine to the monobasic fatty acid ester is 1: 1.02-1.10;

s3, mixing and stirring the synthetic base oil, the saline water, the emulsifier, the calcium oxide, the filtrate reducer and the inert weighting material which are weighed in proportion uniformly to obtain a solution with the density of 1.2-2.8 g/cm³The synthetic base drilling fluid.

Technical Field

The invention relates to the technical field of petroleum and natural gas exploration and development, in particular to a clay-free phase synthetic base drilling fluid and a preparation method thereof.

Background

The oil-based drilling fluid is a drilling fluid system which is composed of oil serving as a continuous phase, water serving as a dispersed phase, and an emulsifier, a shear enhancing agent, a plugging agent, a filtrate loss reducer, alkali and other chemical agents. Compared with water-based drilling fluid, the drilling fluid has the advantages of good lubrication, pollution resistance, high temperature resistance, strong inhibition, oil-gas layer protection and the like, so that the drilling fluid is more and more widely applied to difficult wells such as deep wells, ultra-deep wells, wells with complex structures, special stratum wells, large-displacement horizontal wells and the like.

The suspension problem of the oil-based drilling fluid is always a difficult point, and at present, organic soil is commonly used in the oil-based drilling fluid to improve the flow pattern and improve the suspension capacity. However, the organic soil can reduce the solid phase capacity of the oil-based drilling fluid, pollute low-permeability reservoirs, and is easy to thicken at high temperature, so that the mud performance is deteriorated. Therefore, it is a trend of current development to select a proper flow pattern modifier to replace organic soil to form a clay-free phase oil-based drilling fluid.

Currently, with the increasing number of complex wells and the tightening of environmental regulations, higher demands are being placed on the performance of drilling fluids. The synthetic base drilling fluid is produced under the condition that the water base drilling fluid can not meet the performance requirements of complex conditions under the well and the traditional mineral oil base (diesel oil and white oil) drilling fluid can not meet the environmental protection requirements. The synthetic base drilling fluid has the advantages of low toxicity, biodegradability, no fluorescence and the like on the basis of the advantages of excellent temperature resistance, strong inhibition, good lubricity and the like of the traditional mineral oil drilling fluid, and is widely used in ocean deep water and environment sensitive areas.

Disclosure of Invention

The invention aims to provide a clay-free phase synthetic base drilling fluid which is free of organic soil, simple in formula, strong in emulsion stability, good in thixotropy and low in biotoxicity.

Another objective of the present invention is to provide a method for preparing the above clay-free phase synthetic base drilling fluid.

Therefore, the technical scheme of the invention is as follows:

a clay-free phase synthetic base drilling fluid comprises 60-95% of synthetic base oil and 5-40% of brine by mass, wherein the mass fractions of the synthetic base oil and the brine are 100%; 2 to 6 percent of emulsifier, 0.5 to 1 percent of flow pattern regulator, 2 to 3 percent of calcium oxide, 2 to 3 percent of filtrate reducer and 50 to 500 percent of inert weighting material based on the total weight of the synthetic base oil and the salt water; wherein the content of the first and second substances,

the saline water is a sodium chloride solution, a calcium chloride solution, a potassium chloride solution, a sodium formate solution, a potassium formate solution or a cesium formate solution with the mass fraction of 20-25%;

the emulsifier is compounded by alkyl glucose amide, anionic surfactant and nonpolar solvent; the alkylglucamide is prepared from 27-50 parts by weight of glucose methylamine, 29-43 parts by weight of monobasic fatty acid or fatty acid ester thereof, 9-27 parts by weight of polar solvent and 0.12-0.16 part by weight of sodium alkoxide, and the molecular structural formula of the alkylglucamide is shown as the following formula:

wherein n is any integer of 5-17, and n is an odd number; the polar solvent is C₁～C₄The small molecule monohydric or dihydric alcohol of (a); the anionic surfactant is 1-3 parts by weight of sulfate salt type anionic surfactant; 7-9 parts by weight of non-polar solvent is synthetic base oilThe kinematic viscosity at 40 ℃ is 2-6 mm²A synthetic base oil per second;

in the formulation components forming the emulsifier, the above-mentioned alkylglucamides belong to nonionic surfactants, which are low in toxicity and biodegradable, and are used as raw materials for preparing the alkylglucamides: starch and grease exist in large quantities in nature, belong to renewable resources, and have the characteristics of raw material acquisition and low cost; meanwhile, the glucose chain segment in the alkyl glucose amide molecular chain has a large amount of hydroxyl groups, so that the alkyl glucose amide molecular chain has strong hydrophilicity, has strong surface activity after forming an amide molecular chain with an aliphatic hydrophobic chain segment with a certain length, and can realize the emulsification stability at a lower concentration, so that the alkyl glucose amide molecular chain segment is used as an emulsifier in the synthetic base drilling fluid, and can avoid the defect of poor environmental protection of the traditional emulsifier while playing an emulsification role. The purpose of introducing the nonpolar solvent is to improve the fluidity of the product and facilitate the field charging construction; the anionic surfactant is added to moderately break up intermolecular association formed by the alkyl glucamide due to polyhydroxy, so that the fluidity of the product is increased, and the nonionic/anionic composite surfactant is formed with the alkyl glucamide to achieve the purpose of synergy.

The flow pattern regulator is an alkylglucamide with two glucose chain segments, which is generated by the reaction of dibasic fatty acid with a carbon chain length of 6-18 and methyl ester thereof with glucose methylamine, or an alkylglucamide with a plurality of glucose chain segments, which is generated by the reaction of polybasic fatty acid with a carbon chain length of 10-18 and methyl ester thereof with glucose methylamine; the molar ratio of the amino group of the glucose methylamine to the carboxyl group of the fatty acid is 1: 1.2-1.6; the molar ratio of the amino group of the glucose methylamine to the ester group of the fatty acid methyl ester is 1: 1.2-1.6.

The flow pattern regulator is formed by connecting two or more glucose methylamines to a reaction center of dibasic fatty acid/ester or polybasic fatty acid/ester with a certain chain length to form a polyhydroxy and polyamide-based product taking glucose and a fatty chain as main structures, and the polyhydroxy and polyamide-based product is used as the flow pattern regulator of the synthetic base drilling fluid, not only has low toxicity and easy degradation environmental protection characteristics, but also has a large amount of polar groups of hydroxyl and amide groups on a molecular chain, so that the polyhydroxy and polyamide-based product is easy to associate in a water-in-oil emulsion to form a weak gel form, can effectively increase viscosity in a low flow rate state, and suspends solid particles; under the action of external force such as pumping and the like, the gel state is easy to damage, and the drilling fluid recovers good fluidity, thereby being beneficial to improving the mechanical drilling speed and improving the scouring capability to the well wall; in addition, the structure of the drilling fluid has the characteristics of hydrophilicity and lipophilicity, so that the drilling fluid also has the characteristics of strong surface activity and capability of improving the emulsion stability of the drilling fluid.

Preferably, the synthetic base oil is a gas oil synthetic base oil, a poly α -olefin synthetic base oil, a synthetic ester synthetic base oil, an internal olefin synthetic base oil or a polyether synthetic base oil, the synthetic base oils are prepared by a chemical synthesis or refining method, toxic and harmful substances such as aromatic hydrocarbons are removed, and the synthetic base oils have the properties of environmental protection, good fluidity, no fluorescence, low freezing point and the like.

Preferably, the sodium alkoxide is sodium methoxide or sodium ethoxide.

Preferably, the fluid loss additive is at least one of lignite resin and oxidized asphalt.

Preferably, the inert weighting material is at least one of limestone, barite, hematite.

Preferably, the sulfate ester type anionic surfactant is fatty alcohol sulfate, fatty alcohol-polyoxyethylene ether sulfate, glycerin fatty acid ester sulfate or sulfated sodium ricinoleate. Wherein the fatty alcohol sulfate is fatty alcohol sulfate with carbon number of 12-16, such as sodium dodecyl sulfate; the chemical structural formula of the fatty alcohol-polyoxyethylene ether sulfate is as follows: RO (CH)₂CH₂O)_n-SO₃Na, wherein n is 2 or 3, and R is an alkyl group having 12 to 15 carbon atoms; the glycerin fatty acid monoester sulfate is glycerin fatty acid monoester sulfate with 12-14 carbon atoms of fatty acid, such as sodium glycerin lauric acid monoester sulfate.

Preferably, the polar solvent is at least one of ethanol, propanol, butanol and propylene glycol.

Preferably, the fatty acid or fatty acid ester forming the emulsifier is caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid or stearic acid, methyl caproate, methyl caprylate, methyl caprate, methyl laurate, methyl myristate, methyl palmitate or methyl stearate; the dibasic fatty acid is adipic acid, oxalic acid, dodecanedioic acid, hexadecanedioic acid or octadecanedioic acid; the polybasic fatty acid is a deca-or octadeca-tribasic fatty acid.

A preparation method for preparing the clay-free phase synthetic base drilling fluid comprises the following steps:

s1, adding glucose methylamine and dibasic fatty acid, glucose methylamine and dibasic fatty acid methyl ester, glucose methylamine and polybasic fatty acid or glucose methylamine and polybasic fatty acid methyl ester into a polar solvent, mixing and stirring uniformly, adding a sodium alkoxide catalyst, heating to 130-140 ℃, carrying out reflux reaction for 4-5 hours, then carrying out rotary evaporation to remove the polar solvent in the mixed solution, cooling to obtain a waxy solid, and drying and crushing to obtain a flow pattern regulator product; wherein, the feeding proportion of the fatty acid or the fatty acid methyl ester thereof and the glucose methylamine meets the following requirements: the molar ratio of the amino group of the glucose methylamine to the carboxyl group of the fatty acid is 1: 1.2-1.6; the molar ratio of the amino group of the glucose methylamine to the ester group of the fatty acid methyl ester is 1: 1.2-1.6; the dosage of the polar solvent is 1.9-2.8 times of the total weight of the glucose methylamine and the fatty acid, or 1.9-2.8 times of the total weight of the glucose methylamine and the fatty acid methyl ester; the addition amount of the sodium alkoxide catalyst is 0.1 to 0.21 percent of the total weight of the glucose methylamine and the dibasic or polybasic fatty acid, or 0.1 to 0.21 percent of the total weight of the glucose methylamine and the dibasic or polybasic fatty acid methyl ester

S2, adding glucose methylamine and monobasic fatty acid or glucose methylamine and monobasic fatty acid ester into a polar solvent, uniformly mixing, adding a sodium alkoxide catalyst, heating to 120-130 ℃, performing reflux reaction for 2-5 hours to generate an alkyl glucosamide solution, adding a non-polar solvent and an anionic surfactant while hot, and uniformly stirring to obtain an emulsifier product; wherein the feeding molar ratio of the glucose methylamine to the monobasic fatty acid is 1: 0.8-1.22, and the feeding molar ratio of the glucose methylamine to the monobasic fatty acid ester is 1: 0.91-1.13;

s3, mixing and stirring uniformly the synthetic base oil, the saline water, the emulsifier, the calcium oxide, the filtrate reducer and the inert weighting material which are weighed according to the proportion to obtain the synthetic base drilling fluid with the solution density of 1.2-2.8 g/cm 3.

Compared with the prior art, the clay-free phase synthetic base drilling fluid is prepared by mixing and compounding synthetic base oil, brine, an emulsifier, calcium oxide, a filtrate reducer and an inert weighting material according to a certain proportion, and has the characteristics of increasing the solid phase tolerance of the drilling fluid and improving the mobility under high temperature and high density conditions besides removing the organic soil in a drilling fluid system, so that a better reservoir protection layer can be further obtained.

Detailed Description

The present invention will be further described with reference to the following examples, which are not intended to limit the scope of the invention in any way, in examples 1 to 7, wherein the components are commercially available, and the parts of the components added are specifically parts by weight, and the synthetic base oil of gas oils, synthetic base oil of poly α -olefins, synthetic base oil of synthetic esters, synthetic base oil of internal olefins, or synthetic base oil of polyethers are selected such that the kinematic viscosity (40 ℃) is 2 to 6mm²A commercial synthetic base oil per second.