Study On Determining Method Of Formation Pressure Measurement Parameters While Drilling

In the process of drilling and completion,formation pressure monitoring is a very important work,especially in offshore oilfield operation,while drilling measurement technology has been widely used.In drilling technology,formation pressure measurement mainly uses short pause during drilling to collect pressure and fluid information quickly and obtain formation pressure in real time.In addition to obtaining reservoir pressure and fluidity information,formation pressure measurements while drilling can also be used for real-time mud density management,optimization of drilling and completion operations,safe and effective drilling of high-pressure wells,and accurate formation pressure profiles are conducive to the design and implementation of optimal completion projects.Based on the simplified reservoir model,a typical percolation model is established according to Darcy's law,and the initial and boundary conditions related to formation pressure measurement while drilling are analyzed by referring to the measurement methods of formation pressure measurement instruments such as Geo TAP and Tes Trak.According to the seepage mode in formation pressure testing while drilling,a hemispherical seepage model is established,and the model is solved in spherical coordinate system.The variation law of formation pressure in the testing process is solved,including the law of pressure drop in the swabbing process and the law of pressure recovery after swabbing.Considering the influence of pipeline storage,skin effect and pressure boosting on formation pressure test,the influence degree of each factor on formation pressure test results in different permeability formations is analyzed,and the model is modified accordingly.According to the established seepage mathematical model of formation pressure testing while drilling and the solution results,the analysis method of formation pressure measurement data while drilling is obtained,and the correctness of the theoretical model is verified by analyzing the simulation data and the field test data of existing formation pressure testing instruments.By analyzing the influence of different measurement parameters(swabbing flow rate,swabbing volume,pressure drop duration and pressure recovery time)on response curve,the determination method of measurement parameters used in formation pressure measurement while drilling is preliminarily studied.The analysis of simulation data and field measurement data shows that the error of formation pressure is less than 2% when the theoretical model established in this paper is compared with the result of formation flow analysis(FRA).The error of formation permeability is 4.4% when the permeability is high,and the period of pressure recovery is long in low permeability formation.The 13% deviation between the permeability data and the simulated permeability value proves that the theoretical model is correct and feasible,which lays a solid theoretical foundation for further research on formation pressure while drilling measurement.The research on the determination method of measurement parameters has a certain guiding significance for the development of measuring instruments.