Research On Wellbore Pressure Prediction In The Idle Stage Of Deepwater High Temperature And High Pressure Exploratory Wells

Due to the extremely rapid development of China's economy,the demand for oil and natural gas resources is increasing,but the oil and gas resources on land are far from being satisfied,and the exploration and development of offshore resources,especially deep sea oil and gas resources,are particularly important.The cost of deep-sea operations is extremely high.In order to save the cost of exploration and development,long-term idle exploratory wells can be converted to development wells when conditions permit.The prediction of wellbore pressure during the period when the exploratory wells to development wells are abandoned is important in the early stage of the ring.The gas migration in the wellbore,through the penetration in the cement plug,makes the wellbore pressure rise,which seriously threatens the safe production when the exploratory well is transferred to the development well.Based on the gas seepage theory,a wellbore pressure prediction model was established,and Matlab software programming was used to calculate and analyze the changes in the pressure at the top of each level of cement plugs with time.The rapid increase,the faster the pressure increase at the top of the cement plug closer to the bottom of the wellbore,the later stable a certain level,the greater the pressure value at the top of the cement plug nearer to the bottom of the wellbore.The established pressure model was used to predict the pressure of the DN-2 gas field,and the model was applied to engineering examples.The results show that the solubility of the gas has a greater impact on the early pressure establishment.As the amount of gas increases,the gas dissolution decreases,and later The pressure is stable within a certain range;the greater the comprehensive permeability of the cement ring,the faster the wellbore pressure rises,and the smaller the mud density,the higher the maximum pressure.According to the experimental study of cement permeability,within a week of the experiment,due to the influence of carbon dioxide,the permeability of a single cement sample increased significantly;as the curing time increased,the permeability decreased;under high temperature and carbon dioxide conditions,the permeability decreased significantly.Prediction of wellbore pressure provides a basis for risk assessment of conversion from exploratory wells to development wells,and is of great significance for safe operation of exploratory wells to development wells.