Measurement Procedures and Analysis of Fluid Invasion Drivers During Cement Hydration

摘要

Fluid invasion during cement hydration is governed by, among other factors, differential pressure betweenrnthe formation fluids and the annular fluid. The primary phenomena influencing pressure in the annulus arernevolution of cement slurry physical and chemical properties with time, filtrate lost to the formation, andrnchanges in cement slurry volume during hydration. A successful procedure to design slurries to mitigaternfluid invasion shall model these phenomena and provide viable methods to measure model parameters. Atrnthe same time, it should be feasible to formulate cement slurries to obtain the parameters necessary forrna successful design.rnThis paper discusses model details with emphasis on parameters, their test procedures, and equipmentrndetails. Dynamic filter-cake properties are calculated by applying compressible filtration theory on datarnfrom a modified fluid loss test. Shrinkage/expansion is measured under temperature using the API ringrnmold apparatus. Pressure and displacement response to filtrate loss and shrinkage/expansion is dependentrnon bulk modulus, shear modulus, and static gel strength (SGS) evolution of the cement slurry duringrnhydration. Properties are measured as a function of time using sonic analysis and a rotational gel strengthrndevice. Both material properties and volume changes attributed to fluid loss and hydration showed timerndependency.rnFurthermore, the pressure response of two realistic wells having different permeability and porernpressure profiles is analyzed. The two analyzed wells had different pressure responses, indicating that thernslurry design should be customized for each well. This difference is attributed to varying capabilities ofrnthe well to compensate for volume loss by movement of cement placed adjacent to the permeable section,rnshowing that the relative locations of the filtrate loss and potential fluid influx zones are important. Suchrnan observation is possible only because of the ability to measure and model dynamic properties andrnevents. The proposed methods are practical and can be realized using existing equipment with fewrnprocedural changes. Analysis based on these measurements guides the customization of slurry designs.