Simulation Of Outside Casing Gravel Packing Well Completion In Horizontal Wells

The outside casing gravel packing in horizontal wells in unconsolidated sandstonereservoir a new issue in oil and gas exploitation world, the possible study of which mayconcern rock failure pattern and its recognition, plastic compaction mechanism, packingdynamic simulation. Up to now, it’s a pity that there be no systematic theory and techniquefor outside gravel packing in horizontal wells in unconsolidated sandstone reservoir.Formation rock parameters and stress field around wellbore are the key basic parametersfor the simulation and design of gravel packing in horizontal wells. In this work, an integralmodel is developed to calculate the formation rock parameters along wellbore by the loggingdata. According to the surface rock clastation theory, a new rock strength attenuation model isput forward to calculate the real time rock strength under a certain production time, whichuses strength attenuation factors to indicate the effect of production time and sand productionon the rock strength. Then the model for the stress around wellbore of horizontal wells isevolved. Due to the formation heterogeneity and wellbore trajectory irregularity, it’snecessary to consider the variation of rock parameters and stress around wellbore withwellbore trajectory and production time in the simulation and design of gravel packing inhorizontal wells.In this study, the failure pattern of unconsolidated formation rock is classified into twotypes, one of which is the pattern of fracture initiation and extension, another is plasticcompaction packing. A formation rock failure recognition model is obtain to predict the realfailure pattern of a given formation rock and pumping pressure and rate. With the model, thecritical failure flowing pressure profile along the wellbore trajectory can be clarified to predictthe initial breakdown point.The simulation of outside casing gravel packing is the core issue in this paper. Firstly themechanism and process of formation rock plastic compaction packing in unconsolidatedsandstone horizontal wells under the condition of high pressure injection. Then the area nearthe horizontal wellbore is divided into three areas concerning elastic area, plastic compactionarea and packing area. Accord to Mohr-Coulomb rock failure law and axial symmetry planestrain theory, a systematic model and calculation method for simulation of outside casing gravel packing and prediction of packing area size are set up, which has take the effect of theheterogeneous stress around wellbore on the outside gravel packing behavior intoconsideration.For outside gravel packing of horizontal well, inside casing pack is a necessary step ofthe whole job procedure. A time-dependent numerical simulation model of inside casinggravel packing is developed to visually simulate the inside casing packing process withdeposited sand bed or not. During the process of outside packing, the pumping rate inside thecasing must keep enough value to suspend all of the gravel particles and prevent them fromdeposit. An empirical model for critical pumping rate for all suspension is got by theory andexperiment study, which is used to determine the minimum pumping rate for outside casinggravel packing and provide a basis for the job parameter optimization.Additionally, the mechanism and process of casing inside and outside gravel packing forhorizontal wells in unconsolidated sandstone reservoir are analyzed. Finally, according thetheory and experiment study results, a software package concerning horizontal wells are workout and its application result is analyzed briefly.