Study And Application Of Cementing System In Shale Gas Horizontal Well

Presently, with the increasing demand for energy, unconventional energy proportion in the exploration and development is bigger and bigger. Shale gas is an important unconventional energy, which will become the main direction in future. In the development of shale gas, improving the shale gas well cementing quality is one of the key technologies to guarantee the lifetime of the well, to improve oil recovery and to develop oil and gas fields legitimately. For the use of the oil-base mud in shale gas drilling and high demand for cementing quality when fracturing stimulation, based on the prepared fluid system research, this article aims to develop a suitable flushing fluid for shale gas horizontal well cementing.Interface oil flushing difficulty and inadequate wetting reversal are existing in horizontal shale gas well cementing. In view of the above situation, this paper focuses on studying the flushing fluid system and its evaluation methods, as well as the flushing fluid and spacer fluid rheological model optimization, and designing the pre-flush construction of shale gas XYl-well. The main research work and the main achievements are as follows:(1) On the basis of research evaluation methods of flushing fluid at home and abroad, using the theory of cementing annulus inner wall and the inner wall surface of the new evaluation device sharing the same shear rate, authors have developed a new cementing evaluation method of flushing fluid for oil-based mud. Indoor simulation experiments show that the method can better reflect the flushing fluid efficiency, and can simulate the evaluation of the influence of flushing efficiency of cementing the first or second interface cemented prejudice.(2) Drawing lessons from enhanced oil recovery (EOR) in binary and ternary composite flooding theory, a new type of flushing fluid system which contains surface active agent, emulsifying agent, alkali and inorganic salt has been proposed. Admixture optimization, system evaluation and the action mechanism analysis of the flushing fluid have been done through indoor experiment.(3) Increased density range of spacer fluid system is1.10～2.40g/cm3, and in this range it has a good stability.Setting under different temperatures for8hours, the density difference of spacer is less than0.02g/cm3. Spacer fluid, flushing fluid, oil-based drilling and cement slurry have good rheological compatibility.Weight-loss method showed that spacer fluid and flushing fluid for casing has no obvious corrosion.(4) By optimizing the flushing fluid and spacer fluid rheological models, a model which can describe spacer fluid rheological model more accurate-GHB (Generalized Herschel-Bulkely) model is brought in. According to the specific condition of shale gas XY1-well, application of the paper studies make the reasonable dosage of flushing fluid, spacer fluid and the simulation design of construction.