The SINOPEC Fuling shale gas field is the first large-scale commercial development shale gas field of China, which have been built as a productivity of 5 billion shale gas field until 2015. The problems faced in this location is narrow margin between pore (or collapse)and fracture pressure, therefore the mud loss, collapsing and gas kick are very common problem encountered while drilling, the ROP decreases greatly and the cost of drilling operation increases rapidly. With falling oil and natural gas prices, greater efficiency and excellence in well construction is called for, the MPD related theoretical model and successful use of MPD techniques for improving ROP, controlling gas kick and mud loss, reducing drilling cost for the shale gas horizontal well drilling in Fuling is described. Firstly, a new utility gas kick detect method based on real-time WHP analysis through the theoretical and model analysis was established, in which the WHP variation caused by the tripping, ROP and flow rate variation were taken into account, through which the gas kick can accurately detected as soon as quickly. Secondly, for improving the pressure control precision, a three-layer feedback control method was established and programmed in the controller, through which the bottom hole pressure (BHP) can be adjusted very stable. Moreover, integrated software that combined MPD design and gas kick control simulation was developed based on which the best pressure control procedure and kick initial response can be obtained easily. The MPD technique has been applied in several wells in Fuling shale gas field of SINOPEC, based on the integrated software, the BHP, flow rate, WHP, mud density, and others drilling parameters were all obtained. And through MPD, the drilling results show that the ROP of there wells were improved about 13.9-82%, the outage time have reduced more than 60%. Moreover, through using the low-density drilling mud, the mud loss has been successfully prevented, and also reduced the mud cost. This study will presented the utility theoretical model for MPD gas kick detection, three-layer feedback pressure control method, and the MPD application in shale gas drilling. Through the application of the MPD, the results show that the ROP in shale gas horizontal well drilling has been improved obviously, the optimal oil based drilling mud density was designed has successfully prevented the mud loss and reduced the drilling cost.
It is difficult to meet the safety requirements of the existing well control technology with oil & gas exploration and development to deep complex formation. Therefore, it is important to carry out the analysis and research work of new blow out preventers. The downhole blowout preventer can provide a sealing well near the drill bit, which could eliminate the overflow in the bud. Thus, the downhole blowout preventer will be an additional protect barrier for the existing well control procedure. This paper introduces domestic and foreign downhole BOP situation, and analysis the structure and technical features of these downhole BOPs. The author discusses key technology of downhole BOP on the basis of analyzing the defect of the existing technology. It could be helpful for the research of downhole blowout preventer.
Drilling wells for oil/gas has been increasingly challenging with the companies moving towards difficult environments, such as in Tarim basin of China, some reservoirs buried so deeply (>7,000m) that we experience high temperature and pressure. The problems faced in these locations range from very narrow margin between pore (or collapse) and fracture pressure. The density of drilling fluid is often affected by HTHP, the careful research on the drilling fluids density at HTHP is very important for precisely predicting ESD as well as controlling the downhole pressure. A utility calculation model of drilling fluids density and ESD was proposed, which can predict the HTHP density and ESD. Firstly, a new utility artificial neural network HTHP drilling fluid density prediction model was established based on the traditional BP neural network and PSO (Particle Swarm Optimization) optimization method. Then PSO-BP neural network HTHP drilling fluid density prediction model was proposed, in which the influence of drilling fluid component (oil phase, water phase volume fraction) was taken into account. Available experimental measurements of water-based and oil-based drilling fluids at pressure ranging from 0-96MPa and temperatures up to 183°C were used to develop and the PSO-BP network model and then the network weights, threshold parameters. Through this model the high-precision HTHP drilling fluids density can be obtained easily with the knowledge of the drilling fluids component data (oil phase and water phase volume fractions) and its density at standard conditions(0MPa, 20°C) based on the basic principle of PSO-BP network. Moreover, an new comprehensive ESD calculation model of HTHP well was established, which is applicable for all common type drilling fluids and through we can obtained the ESD profile of the well easily. The prediction of this model has been compared with an extensive set of data from literature, the comparisons of different fluids density in HTHP show very good agreement, the prediction accuracy was improved, and in which the maximum average absolute error of predictions is less than 0.005sg. Finally, the proposed model has been applied for HTHP drilling fluids density and ESD prediction in several wells of the Tarim basin in China, the results show that the proposed model can exactly provide the HTHP drilling fluids density and ESD profile. This study proposed an utility calculation of HTHP drilling fluids density and ESD profile while drilling, based on the new PSO-BP neural network, the optimal network weights, threshold parameters of was obtained, through which the high-precision drilling fluids density and ESD can be obtained easily. Moreover, the model has been verified and applied for field monitoring. Therefore, this model can be applied to provide more accurate predictions of HTHP drilling fluids density and ESD while drilling.
The equipment commonly used in managed pressure drilling (MPD) allows alternative responses to kicks that do not need to stop the pump or shut in the well. The pivotal issue of kick control for MPD is the early gas influx detection and the optimal initial response when the kick was detected during drilling. The careful research on gas influx detection and the corresponding control method is very important. Firstly, the valve opening, bottom hole and well head pressure variation characteristics were analyzed based on the real-time measured data, and then the valve opening and pressure signature of gas influx for different MPD modes (CBHP, CWHP, MFC) was obtained based on the theoretical and model analysis, in which the pressure variation caused by the tripping, ROP and flow rate variation were taken into account, through which the gas kick can accurately detected as soon as quickly. Secondly, the influence factors for initial response selection of kick control was analyzed, and then the comprehensive optimization schedule of response for kick control was established, in which several factors were took into account, such as formation characteristics, drilling conditions, influx intensity and so on, through which the best mode for kick control can be obtained easily. Moreover, integrated software that combined kick detection and gas kick control simulation was developed based on which the best pressure control procedure and kick initial response can be obtained easily. The gas influx detection and control technique has been applied in Fuling shale gas field of SINOPEC, which is the first large-scale commercial development shale gas field of China. The results show that we can make precisely gas detection based on the new early gas influx detection method and the kick can also be control very well based on the optimization method. Based on the proposed method for kick detection and control, the NPT have been reduced more than 60%. This study will presented a novel gas kick detection theoretical model for all common MPD modes, and the gas influx control optimal procedure. Through the field application in shale gas drilling, the results show that the NPT has been reduced obviously, and the optimal kick control was designed has successfully prevented the serious kick and reduced the drilling cost.
A generalized hydraulic model that is independent of the rheological model is presented for non-Newtonian fluids flow in pipes. The generalized model was developed without assuming that the generalized flow index (n') remains constant over all shear rates. Based on the pipe flow control equation, the explicit equations between the wall shear stress and volumetric flow of all common rheological models flowing in pipe were obtained, such as the Casson model, HerschelBulkley model and the Robertson-Stiff model, and they all can be solved numerically to obtain the accurate wall shear rate and shear stress. We give the theoretic calculation method of n' for all time-independent non-Newtonian fluids. This method is applicable to all common rheological models without the assumption that n' is constant. Moreover, we derived the general expression of generalized Reynolds number and then gave a utility pressure loss calculation model. A set of measured hydraulic data were utilized to evaluate this model. The results show that it can precisely calculate pipe flow parameters for all types of different non-Newtonian fluid. The proposed model will lay a foundation for the application and more extensive use of complex but more precise rheological models in engineering.
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