Research Of Thixotropy Spacer System

During the displacement of drilling fluid in cementing practice, the pHysical contact of cement slurry and drilling fluid can easily result in varying degrees of cross contamination with the company of cement contamination in drilling fluid. The application of spacer fluid can effectively isolate the drilling fluid and cement slurry so as not to cause cross contamination. In leakage zone,in order to guarantee the cementing quality,we need a thixotropic spacer. In that aim, we conduct a series of experiments about the thixotropic spacer.Based on the basis of the literatures investigation, first, optimize the thixotropic agent, thixotropic agent is the cross-linked polymer system. The polymer select guar gum and the crosslinker select organic boron.Through laboratory tests,we know that the conditions while thixotropy and rheology of thixotropic agent maintaining the best:the concentration of HPG is 0.3%, the value of pH is 9, the dosage of crosslinker is 0.09%.we optimize the suspension stabilizer and the heavy weight additive. we formed a kind of thixotropic spacer system that can adjustable density form 1.1 g/cm3 to 2.4g/cm3 (Through change the dosage of suspension stabilizer).The system has a good thixotropy, rheological property and suspension stability; the thixotropic spacer can be well compatible with cement slurry and drilling fluid, and can lower the drilling fluid viscosity for easier displacement of drilling fluid, and improve the rheological property, and no pHenomenon of flocculation. It will not shortage the thickening time of cement slurry, not do harm to well cementation and will not increase the filter loss of cement slurry. Also it will decrease the compressing strength of cement stone.Moreover, in view of the fractured formations, a new kind of thixotropy spacer is developed by the optimization of bridge material and its mixing with spacer. Evaluation is also conducted for the fundamental performance and sealing effect of thixotropy spacer. Experiments demonstrate that the thixotropy spacer presents practical application importance in safety assurance in absorption wells and in improving the in-situ cementing quality.