Evaluation mud cake for shale water-based drilling fluid blocking performance and preparation method

Abstract

The invention relates to an evaluation mud cake for shale water-based drilling fluid blocking performance and a preparation method. An effective blocking agent can be preferentially selected to evaluate shale well water-based drilling fluid blocking performance. According to the technical scheme, the evaluation mud cake is prepared from 100 g of barite, 10 g of polyacrylamide, 50 g of sodium polyacrylate, 200 g of API barite, 7 g of a hydrophobic associated polymer and 1000 g of tap water. The preparation method includes the steps that firstly, 1000 g of tap water is weighed, 100 g of barite is added under low-speed stirring, and high-speed stirring is carried out for 30 min; then, 10 g polyacrylamide is added, and high-speed stirring is carried out for 30 min; 50 g of sodium polyacrylate is added, and high-speed stirring is carried out for 30 min; 200 g of API barite is added, and stirring is carried out for 30 min; finally, 7 g of the hydrophobic associated polymer is added, stirring is carried out for 30 min, the mixture is put into a vessel of a water loss meter, pressing is carried out for 2 h at the pressure of 3.5 Mpa and the normal temperature, and the evaluation mud cake is obtained. Only a few kinds of raw materials are used at a low dose for preparing the evaluation mud cake, and the evaluation method is simple and efficient.

Description

technical field [0001] The present invention relates to a mud cake and its preparation method for evaluating the plugging performance of water-based drilling fluid when drilling into shale. According to the method, the mud cake is thin and dense, and its permeability can reach the order of magnitude of shale formation, especially It is suitable for evaluating the plugging performance of water-based drilling fluid in shale wells. Background technique [0002] Due to the well-developed fractures and strong water sensitivity in shale formations, problems such as lost circulation, collapse, and diameter shrinkage are particularly prone to occur in long horizontal section drilling, and drilling fluids are required to have a good plugging effect. Therefore, the evaluation of shale plugging effect has become another new topic in shale gas development. [0003] In order to maintain the wellbore stability of horizontal wells in shale reservoirs, the most effective measure in foreign...

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Problems solved by technology

[0005] The purpose of the present invention is: in order to overcome the problem of wellbore instability caused by fracture development and strong water sensitivity when using water-based drilling fluid to drill into shale formations, suppress The hydration and collapse of the shale formation can optimize the effective plugging agent. For this reason, a mud cake and preparation method for evaluating the plugging performance of shale water-based drilling fluid are provided for simulating the shale formation, so as to achieve the optimum plugging agent plus Measurement and evaluation of plugging performance of shale water-based drilling fluid

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