阅读说明：本技术 油基钻井液钻遇高价盐地层盐结晶析出的处理方法 (Treatment method for oil-based drilling fluid to crystallize and separate out salt in high-salt stratum ) 是由 范劲 冉启华 张坤 李茂森 葛炼 欧猛 彭碧强 刘政 罗宇峰 肖沣峰 李俊材 于 2020-05-13 设计创作，主要内容包括：本发明公开了一种油基钻井液钻遇高价盐地层盐结晶析出的处理方法,由如下步骤构成：a、配制氯化钙溶液,加入油基钻井液中,循环时长4~6h；b、配制硫酸钠溶液,加入油基钻井液中,循环时长1~2h；c、配制高价盐重结晶抑制剂溶液,加入油基钻井液中,循环时长1~2h；d、循环钻井液2h以上,保证油基钻井液破乳电压大于400V；e、取油基钻井液总体积量10%~15%的基础油,在基础油中加入3%~5%乳化剂,充分搅拌2h以上配制成基础油基液,配制完成后加入油基钻井液中,循环油基钻井液4h以上。本发明能够很好的解决油基钻井液高价盐析出结晶的难题,保证遇到此类复杂问题后可以顺利恢复钻进。(The invention discloses a treatment method for salt crystallization and precipitation of a stratum with high-valence salt when an oil-based drilling fluid is drilled, which comprises the following steps: a. preparing a calcium chloride solution, adding the calcium chloride solution into the oil-based drilling fluid, and circulating for 4-6 hours; b. preparing a sodium sulfate solution, adding the sodium sulfate solution into the oil-based drilling fluid, and circulating for 1-2 hours; c. preparing a high-valence salt recrystallization inhibitor solution, adding the high-valence salt recrystallization inhibitor solution into the oil-based drilling fluid, and circulating for 1-2 hours; d. circulating the drilling fluid for more than 2 hours to ensure that the demulsification voltage of the oil-based drilling fluid is more than 400V; e. taking base oil with the total volume of 10-15% of the oil-based drilling fluid, adding 3-5% of emulsifier into the base oil, fully stirring for more than 2 hours to prepare base oil base fluid, adding the base oil base fluid into the oil-based drilling fluid after preparation, and circulating the oil-based drilling fluid for more than 4 hours. The method can well solve the problem of crystallization of the oil-based drilling fluid by high-price salt precipitation, and ensures that drilling can be successfully recovered after the complex problems are met.)

1. A treatment method for salt crystallization and precipitation of a stratum with high-valence salt in drilling of an oil-based drilling fluid is characterized by comprising the following steps:

a. preparing a calcium chloride solution with the concentration of 25-30%, wherein the calcium chloride solution accounts for 2-3% of the total volume of the oil-based drilling fluid, adding the calcium chloride solution into the oil-based drilling fluid, and circulating for 4-6 hours;

b. preparing a sodium sulfate solution with the concentration of 0.5-1%, wherein the sodium sulfate solution accounts for 1-1.5% of the total volume of the oil-based drilling fluid, adding the sodium sulfate solution into the oil-based drilling fluid, and circulating for 1-2 hours;

c. preparing a high-valence salt recrystallization inhibitor solution with the concentration of 20-30%, wherein the high-valence salt recrystallization inhibitor solution accounts for 2-3% of the total volume of the oil-based drilling fluid, adding the high-valence salt recrystallization inhibitor solution into the oil-based drilling fluid, and the circulation time is 1-2 hours;

d. circulating the drilling fluid for more than 2 hours to ensure that the demulsification voltage of the oil-based drilling fluid is more than 400V;

e. taking base oil with the total volume of 10-15% of the oil-based drilling fluid, adding 3-5% of emulsifier into the base oil, fully stirring for more than 2 hours to prepare base oil base fluid, adding the base oil base fluid into the oil-based drilling fluid after preparation, and circulating the oil-based drilling fluid for more than 4 hours.

2. The treatment method for salt crystallization of high-valence salt formation encountered by oil-based drilling fluid drilling according to claim 1, wherein the treatment method comprises the following steps: the recrystallization inhibitor is nitrogen tritium triacetamide.

3. The treatment method for salt crystallization of high-valence salt formation encountered by oil-based drilling fluid drilling according to claim 2, wherein the treatment method comprises the following steps: the base oil is white oil or diesel oil.

4. The treatment method for salt crystallization of high-valence salt formation encountered by oil-based drilling fluid drilling according to claim 3, wherein the treatment method comprises the following steps: the emulsifier is amide ester.

Technical Field

The invention relates to a treatment method for salt crystallization and precipitation of a high-salt stratum when an oil-based drilling fluid is drilled, which is applied to the petroleum and natural gas drilling industry.

Background

With the increasing of the difficulty of oil gas exploration and development, the geological condition is more and more complex, the oil-based drilling fluid has the advantages of better performances such as inhibitive performance, lubricating performance and the like than the water-based drilling fluid, strong anti-formation fluid pollution capacity and the like, and the oil-based drilling fluid is widely applied to high-difficulty complex wells such as risk exploration wells, shale gas horizontal wells and the like. In the process of drilling a risk exploratory well, various pollution sources exist in the stratum to pollute the drilling fluid drilling the stratum to be met, and the oil-based drilling fluid drilling meets soluble high-price salt (such as Ca)²⁺、Mg²⁺、Ba²⁺Etc.) after the formation, the salt quickly reaches a supersaturated state in the water phase due to the lower water phase content in the oil-based drilling fluid, and in the upward returning processCrystallization is separated out along with the temperature reduction in the shaft, and the salt crystallization easily causes the pump pressure to rise, the drilling tool to be worn and stuck, and the normal drilling is influenced. For example, after a ST6 well in Sichuan area is drilled in a high-salt stratum by using the oil-based drilling fluid, salt crystals are separated out at the positions of drill pipe filter paper and the diameter-variable positions of a drilling tool, so that normal drilling cannot be performed.

Disclosure of Invention

The invention aims to overcome the problems in the prior art and provides a treatment method for salt crystallization and precipitation of a stratum with high-valence salt in an oil-based drilling fluid. The method can well solve the problem of crystallization of the oil-based drilling fluid by high-price salt precipitation, and ensures that drilling can be successfully recovered after the complex problems are met.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a treatment method for salt crystallization and precipitation of a stratum with high-valence salt in drilling of an oil-based drilling fluid is characterized by comprising the following steps:

a. preparing a calcium chloride solution with the concentration of 25-30%, wherein the calcium chloride solution accounts for 2-3% of the total volume of the oil-based drilling fluid, adding the calcium chloride solution into the oil-based drilling fluid, circulating for 4-6 hours, and dissolving precipitated salt crystal;

b. preparing a sodium sulfate solution with the concentration of 0.5-1%, wherein the sodium sulfate solution accounts for 1-1.5% of the total volume of the oil-based drilling fluid, adding the sodium sulfate solution into the oil-based drilling fluid, circulating for 1-2 hours, and precipitating and removing free high-valence ions in a water phase of the oil-based drilling fluid;

c. preparing a high-valence salt recrystallization inhibitor solution with the concentration of 20-30%, wherein the high-valence salt recrystallization inhibitor solution accounts for 2-3% of the total volume of the oil-based drilling fluid, adding the high-valence salt recrystallization inhibitor solution into the oil-based drilling fluid, and the circulation time is 1-2 hours, so that salt in a stratum is inhibited from entering the oil-based drilling fluid and then continuing to separate out;

d. circulating the drilling fluid for more than 2 hours to ensure that the demulsification voltage of the oil-based drilling fluid is more than 400V;

e. taking base oil with the total volume of 10-15% of the oil-based drilling fluid, adding 3-5% of emulsifier into the base oil, fully stirring for more than 2 hours to prepare base oil base fluid, adding the base oil base fluid into the oil-based drilling fluid after preparation, and circulating the oil-based drilling fluid for more than 4 hours.

The recrystallization inhibitor is nitrogen tritium triacetamide.

The base oil is white oil or diesel oil.

The emulsifier is amide ester.

The invention has the advantages that:

1. when salt crystals appear in the oil-based drilling fluid, the water phase content of the oil-based drilling fluid is firstly improved, blocky crystals of partial salt are dissolved, the amount of blocky crystals in the drilling fluid and at the reducing position of a drill rod is reduced, the drilling fluid is recycled, and conditions are provided for the next step of treatment. After the water phase content is increased to dissolve part of salt crystals, sulfate ion precipitation is further introduced to remove free barium ions in the drilling fluid, and sufficient sulfate ions enable the reaction balance to be carried out in the direction of generating the precipitation, so that salt crystals of the oil-based drilling fluid are completely removed. After salt crystals in the drilling fluid are removed, barium ions in the stratum can continuously enter the drilling fluid in the drilling circulation process of the oil-based drilling fluid, and therefore the barium ions entering the drilling fluid are inhibited from crystallizing out by adding a salt recrystallization inhibitor. After the treatment, the problem of salt crystallization is solved, but the performance of the oil-based drilling fluid is affected, so that the performance of the oil-based drilling fluid needs to be optimized and adjusted by adding a proper amount of base oil base fluid, and normal drilling is recovered.

2. The method is an emergency treatment measure after crystal precipitation, is different from a prevention measure, is simple in implementation process, high in field treatment efficiency and good in effect, and can be used for wells drilled by oil-based drilling fluid, such as risk exploratory wells, complex deep wells and the like.

3. Along with the increasing of complex deep wells, the probability that the oil-based drilling fluid drill meets high-price salt strata is increased, salt crystallization can abrade a drilling tool and cause drill sticking easily, the method can well solve the problem that the oil-based drilling fluid high-price salt is crystallized, and smooth recovery of drilling can be guaranteed after the complex drilling is met.

Detailed Description