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Proper planning and front-end engineering, in a Biphasic MPD operation to drill a high temperature depleted reservoir in Mexico south area, demonstrated the real added value of the Constant Bottom Hole Pressure (CBHP) technique to overcome risks associated with a nuisance gas zone, hole cleaning and geo-mechanic issues which caused the loss of the original 5 7/8?? hole by failure of the BHA during a pipe work operation in tight hole. Annular velocity is considered as the most critical factor affecting hole cleaning condition in a high angle well in the absence of pipe rotation and cuttings bed deposition is an escalating problem to be overcome too. This situation is aggravated when a biphasic system is used, because density, phase and viscosity change with pressure and temperature in multiphase flows. Also, flow regimes in multiphase flow are more complex, and do not lend themselves to simple characterizations such as laminar and turbulent flow and they are dependent upon the angle of inclination as well as the phase behavior of the fluids. On this way, the velocity of the fluids, the temperature of the surrounding formation, geometry, inlet temperature, specific heat of the fluids and surrounding material among others impact the temperature profile. A complete MPD program that included flow chart decision trees associated with all lessons learnt from the original hole was performed, to improve hole condition through operational practices but also to handle gasification while drilling and tripping. In addition to this, a Hazard Analysis and Risk Control (HARC) was done as well as all contingency plans to mitigate and/or avoid these high potential problems. Thanks to an elaborated MPD program, state-of-the-art equipment, constant adaptation of the fluctuating conditions of the open hole and experienced decision makers, the side track using low head MPD was successfully performed to drill and complete an un-drillable deeper well with minimum operational problems, increasing the production of this mature field.
Wells drilled with nitrified drilling fluids require a solution for the transmission of measurement-while-drilling (MWD) surveys, bi-directional communication with rotary steerable systems, and transmission of MWD and and logging-while-drilling (LWD) measurements of downhole temperature and annular pressure for surface choke adjustments. Wired drillpipe (WDP) provides the solution for these requirements. Results from a recent well drilled into an underpressured reservoir in southern Mexico provided an opportunity to demonstrate the applicability of WDP to deliver the required measurements and maintain the proper directional control while keeping the well fluids under control. During WDP operations, both the traditional mud pulse transmission and the new WDP transmission methods are available, providing 100% reliability for receiving the downhole MWD/LWD data.During the drilling of this well, both single and multi-phase Managed Pressure Drilling (MPD) techniques were used. The plan called for the overburden and reservoir sections to be drilled in one bit run but with different mud types and constant bottomhole pressure (BHP). Before drilling the reservoir section, the single-phase mud used to drill the overburden had to be changedover to multi-phase mud while monitoring the wellbore for signs of instability. Maintaining constant BHP in this type of MPD operation is complicated by the fact that current hydraulic models do not have the proven capability to support constant BHP in a nitrified OBM.With mud pulse telemetry, downhole data transmission stops when the rig pumps are shut-down. But with WDP, downhole data is actively transmitted during the time between pump shut-down and pipe disconnection. This allows MPD personnel to monitor actual annular pressure during pump transitions and more accurately determine the optimum choke position for constant BHP. During the connection, the downhole annular pressure is stored in memory. Once the connection has been made the data is transmited up-hole for evaluation and analysis, which provides immediate feedback on the stability of the BHP during the connection.Pressure sensors (along string measurements or ASM) within the multiple WDP repeater subs allow us to compute the fluid density at multiple intervals along the annulus for the first time in the history of drilling. We document a rather surprising case of temperature effects overriding pressure effects during the use of a single-phase compressible OBM used in the first stage of this drilling operation. This has implications for using WDP measurements to calibrate and verify hydraulic models for both single and multi-phase drilling fluids. Proper hydraulic modeling capabilities are critical for MPD operations.This well provides the opportunity to demonstrate other applications for these newly invented "interval fluid densities." For example, they are used to verify the top of the fluid level with and without the presence of nitrogen injection when accurate flowin versus flow-out measurements are not available. This is ...
The well used for this study, 301, was originally considered "un-drillable". A steep pore pressure ramp combined with loss zones resulted in a cross-flow environment that was very difficult to control, as the drilling window was effectively reduced to less than 0.09g/cc. The ability to precisely control the pressure profile in the annulus is one distinct advantage of Managed Pressure Drilling (MPD). In worst case scenarios with very narrow pore pressure and fracture gradient windows, the tight drilling margin may require the use of an automated MPD system. The system can precisely apply surface back pressure to maintain a balance of flow into and out of the well by maintaining a constant bottom hole pressure and replacing the friction pressure losses in the annular space when the rig pumps are off.During the execution of the well 301, all Automated MPD benefits were applied (Dynamic FIT's, Dynamic Flow Checks and CBHP control) to detect and control kicks, identifying and control ballooning effects and maintaining the bottom hole pressure within the high pressure tight window between 2.426 and 2.451 g/cm 3 . Proper selection, configuration and continuous calibration of the hydraulics simulations during drilling operations was critical to drill the production section and successfully reach target depth. This paper presents the hydraulics modeling during the planning phase and techniques used during execution with the automated MPD system. Following two previous failed attempts, the 301 well was the first successful well to penetrate the reservoir in the Camaronero field, proving automated MPD as a successful drilling technique for this field.
This document presents the successful application of pro-active Managed Pressure Drilling (MPD) to drill one section through three different sands; the one in the middle with a low fracture pressure, the lower sand with a formation pressure higher than the frac gradient of the weak formation. The wrong decision to apply MPD in a reactive way leads to NPT, influxes, mud losses and increased risks. It is shown how the conventional procedures to drill and make the trips are replaced by tailored MPD procedures leading to successful results. The Client understands the high value of proactive MPD, not only to drill but also to during trips. The drilling commenced with a MW of 1.6 g/cc and after 100 m the MW was increased to 1.62 g/cc (it is a routine procedure in the field to increase the mud density prior to reaching the expected high pressure zones while drilling conventionally). Some meters after start drilling the low frac gradient sand total mud losses were observed. The MW was reduced from 1.62 to 1.52 g/cc and MPD was implemented in a proactive manner whereby the BHP was maintained constant. The big challenge was to control the well at all times avoiding a catastrophic condition.
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