Abstract
Tremendous amounts of oil and gas reservoir are located in ultra-deep formations, such as Shunnan block in Tarim basin of China, some reservoirs buried deeper than 8000m and which are major exploration areas of SINOPEC. The formation geological conditions are complicated, multiple pressure systems co-exist in the same borehole, narrow pressure-margin problems, all above may cause down-hole troublesome conditions while cementing, such as leaking, fracturing formations and so on. And the managed pressure cementing (MPC) was selected for solving the above problems. But the key for a successful MPC depend on accurate, real-time knowledge of dynamic parameters calculation. Therefore, a real time dynamic parameters calculation for MPC is very important.
Firstly, a comprehensive real-time hydraulic calculation method for cementing replacement process was established, in which the difference of density, rheological properties, location and length of different fluids were taken into account. In order to improve the calculation precision, the flow channel both in pipe and annuli was divided into several sections, through which the different diameters of the channels were considered. Secondly, according to the density contrast of operating fluids, a vacuum (U-Tube effect) will appear at the inlet in the cementing replacement process, an integrated U-Tube effect analytical model was established based on the Euler equation, in which the influence of well deviation was taken into account too, and though which the height and volume of vacuum, the down-hole operating fluids acceleration, the out flow rate variation et al. all can be accurately calculated and simulated. Moreover, a series of system calculation software were developed to predict cementing fluids position, fluids acceleration, flow pressure drop, BHP, expected WHP and the related control parameters for MPC.
The proposed model has been applied in HPHT ultra-deep well MPC operation of SINOPEC Northwest oil filed in Traim basin, there is an excellent match between the calculated and measured data. Furthermore, this simulation software has been used for designing the MPC parameters, and it runs smoothly with convenient operation. Therefore it can be seen this system can be applied to provide more convenient fast and precise dynamic parameters monitoring for MPC.
This study proposed a novel model of Cementing dynamic parameters calculating and developed a comprehensive real-time monitoring system for MPC. Through the application of the monitoring, we can adjust the cementing parameters in real time while MPC, and this real-time monitoring has been applied in several wells very well. Therefore, this study is novel and can afford an effective approach to improve cement quality.
A Method for Calculating Dynamic Parameters of Intersatellite Link Signals
