Study On Damage Of Clastic Rock Reservoir By Cementing Cement Slurry

In the process of cementing, the solid particles and filtrate in the cement slurry will spread, penetrate into the reservoir, thereby sealing the reservoir pore throat, causing serious damage to the reservoir. By now many domestic and foreign scholars have studied this issue, but the extent and depth of damage to the reservoir, different researchers have inconsistent conclusion, making the current understanding of cement slurry on reservoir damage confusion about.Thesis put the universality of characteristics of clastic rock reservoir research as a starting point, and the medium porosity and permeability sandstone reservoir of YH23 block for a certain oilfield as the research background, to carry out the cement slurry of clastic reservoirs damage research. According to the characteristics of cement slurry, from clastic rock reservoir lithology and physical property characteristics to pore throat characteristics and the characteristics of temperature and pressure are analyzed, furthermore thise paper analyzed the aspects such as potential damage factors from the clay minerals content, formation fluid properties and solid slurry characteristics of the reservoirs, it finally get the potential damage factors of YH23 block, mainly includes sensitivity damage, damage inorganic scale precipitation and cement slurry solid particle plugging damage, etc.There is no research for the cement slurry reservoir damage evaluation method, considering the process of cementing leakage and no leakage in both cases,thesis examines the applicability of the current drilling mud damage evaluation method to the cement slurry damage evaluation. It is concluded that under the condition of the cementing leakage, the slurry can be used in direct contact way to evaluate its damage degree of reservoir cores. Under the condition of cementing no leakage, need to consider to two cases which is have mud cake or not have mud cake that formed by drilling fluid to evaluate its damage degree; In view of the damage characteristics of cement slurry to reservoir, the speed of the reservoir sensitivity, water sensitivity, salt sensitivity, alkali sensitivity and stress sensitivity is evaluated;In view of YH23 block reservoir, by simulating and studying the cementing leakage and no leakage conditions of damage degree to the reservoir caused by cement slurry: Under the condition of cementing leakage, the average damage degree of the reservoir was up to 40.07%, it is a severe damage; Cementing no leakage conditions, with external mud cake conditions,the cement slurry secondary pollution harm rate to an average of 26.03%, without external mud cake conditions,the cement slurry secondary pollution harm rate to an average of 37.20%, it is showed that the drilling external mud cake influence the cement slurry damage on reservoir; Through cement slurry filtrate and formation water compatibility study and combined with CT scan and XRD analysis techniques, finally proven the damage mechanism that the slurry solid phase particles and the filtrate caused to the clastic rock reservoir; The depth of the cement slurry filtrate invasion in the YH23 block reservoir is 20.6 cm, it can be lifted by perforation, it is calculated that under the cementing no leakage conditions,the cement slurry is not the main reason for the reservoir damage.Based on the research results in the formation of a series of experiments from a core set of procedures and methods and the final selection process to evaluate the mechanism of damage, the method can be applied to the cement slurry damage evaluation experiment to non-clastic reservoirs. At the same time, As a result of the limitation of experimental conditions, this paper only considers the static condition of the cement slurry damages, the next step can be focuses on the dynamic conditions cement slurry damage reservoir evaluation methods and laboratory equipment.