The Effect Of Oil-based Drilling Fluid Filter Cake On The Cementation Strength Of The Two Interface

The filter cake acted as curing layer was formed around the wall surface in the process of oil-base drilling fluid cementing, which affected bonding strength of the cement slurry and borehole wall and the quality of oil-base drilling fluid cementing. It was of great significance to investigate the influence of oil-base drilling fluid filter cake on the interface cementation strength, effective cleaning and reversing-wetting ability to improve the quality of oil-base drilling fluid cementing. But most researches focused on the formation and properties of filter cake from the drilling consideration instead of the interface bonding strength to study the property, structure and solution of filter cake. Therefore, aimed at to settle the oil-base drilling fluid cementing problem of the tarim gas well, the thickness, strength, micro structure and the structure of hierarchical of oil-base drilling fluid filter cake were characterized to clarify the influence of filter cake on the second interface cementation strength. Explore the influence degree of the performance of the filter cake to the interface cementation quality, influence mechanism and the solving measures, it is a key point to improve the cementing quality of oil-base drilling fluid to discuss the effect of the filter cake on the interface cementation quality and mechanism and the solving measures. Based on the analysis of experiments and theoretical research, it was concluded as follow.(1) A filter cake strength test method is developed to meet the demands of research on the basis of previous studies. It realized the test of core filter cake (surface) and the filter cake (plane) strength, which could measure the strength of filter cake layer by layer to study layered structure of filter cake. The relationship between the strength of filter cake and the bonding strength from the perspective of the cementing was built through the cementing strength experiment of core obtained after the previous test.(2) The layer structure of oil-base drilling fluid filter cake was studied from macroscopic and microscopic aspects via filter cake strength tester and Micro-CT analysis. It was found that the filter cake strength showed an increase from outer to inner from macro, which could be divided into three intensity ranges. The microscopic analysis also exhibited that the filter cake showed density differences causing three kinds of color layer, which proved the layered structure of filter cake.(3) In this paper, properties and chemical composition of the oil-base drilling fluid filter cake were studied. It was concluded that BaSO4 (barite) and kaolinite (organic soil) were the main phases named as the soild phase particles and crossliner substance, respectively. And it was found that weighting agent and organic soil brought about great influence on the strength of filter cake.(4) The influence of thickness, strength and wetting-ability of the filter cake on the bonding strength was explored on the basis of above research about filter cake. It was proved that the cementation strength was affected by the thickness and the strength of the filter cake. High strength of the filter cake could compensate the negative effect of filter cake on the cementation strength, which meat that the low strength of filter cake layer displayed negative influence on the strength of cement. Moreover the cementing strength increased along with the hydrophilic enhance of filter cake surface.(5) The role of surfactant in filter cake cleaning and reversal wetting-ability was cleared on the basis of the above researches. Targeting to the shortcomings of surfactant performance, the preferred and optimization method of high efficient surfactant was established according to the characteristics of surfactant. Furthermore surfactant systems with high performance were successfully selected by this method.