Formation Pressure Calcullation Method For Density Drilling Well

Daqing oilfield is a continental deposit sandy reservoir. Its formation is made non-homogeneous sandstone and mudstone. Through the water-flooding development in a long time, formation void pressure has a great change in profile. It results some contradictories. Among the layers and in one layer the variable sedimentary models. Formation void pressure distribution is a kind of very important data for adjusting oil production well drilling plan.Nowadays, in Daqing oil fields the commonly used methods to acquire formation void pressure are as follow: According to the data of water injection wells and oil production wells, calculating the resulting pressure of the perforated formation; measuring the resulting pressure of the perforated formation of a well after the well shutdown for a certain period. The result of all these measuring is dynamic resulting formation void pressure, not the required single layer dada. The only measuring method to get a single layer pressure is to test a single formation pressure repeatedly on a naked well, but the drawbacks are that it is very expensive and will slow down the drilling process. So it is not widely used. On this research, a new method has been developed to for predicting pressure difference based on a thorough study on the relation between the invasion radius and invaded zone, pressure difference and the radial resistivity changes of the reservoir. Meanwhile, in the naked well, a fluid log-well has been done to check the mud change on the base of its change. The log curve has a change so we can discuss the non-normal formation. The method has four advantages as follow:(1)It needs not any extra investment;(2)it will not delay the oil development and the period of drilling;(3)Through digitalized log-well data, single well pressure profile can be calculated automatically;(4)Through the map of the single formation fluid pressure potential, water drive direction and water drive area of reservoirs can be fixed. This method has been tested on site in Daqing Saertu oil fields and the practical datas fits perfect well with the theoretical ones generated by the model in this method. At the same time, one enhanced oil recovery method through changing the pressure of production wells is proposed .All of these provide a solid foundation to adjust oil-developing plan.The move effective result is to make safety drilling operation and improve the cement quality by using this technical drilling measure. In the same time, avoiding to using high mud weight, which causes more complicated down hole condition reduce the drilling cost, improve the cement quality and disease the contamination to the reservoir from drilling operation. The technical measure can be used in whole adjusting drilling block in Daqing oil fields.