An operator considered using Constant Bottomhole Pressure (CBHP) Managed Pressure Drilling (MPD) in the evaluation phase of a drilling project and decided not to go forward with MPD. While drilling the well, unfortunately, they had a well control event that required an increased mud-weight ultimately resulting in a differentially stuck-pipe condition.
MPD services were exclusively called to help free this differentially stuck pipe/BHA. MPD provided enough flexibility to deliberately reduce the wellbore pressure below pore-pressure and decrease the differential pressure to free the stuck pipe/BHA. Using CBHP variation of MPD resulted in unsticking the pipe as explained in this case history. The detected influx was circulated out with appropriate pump rate (high flow rate) using MPD equipment. The operator drilled forward with the assistance and additional protection of MPD to reach the Targeted Depth (TD) without having further issues in a very narrow drilling window. This successful field operation shows that CBHP MPD can indeed be used to precisely manage the annular pressures, as elaborated in the IADC’s MPD definition, and safely and successfully solve some of the baffling problems of the drilling industry.
Nauduri, Sagar (Pruitt Optimal) | Parker, Martyn (Pruitt Optimal) | Nabiyev, Akram (Pruitt Optimal) | Sampley, Eddy (Pruitt Optimal) | Kirstein, Lenord (Pruitt Optimal) | Morris, Jason (Pruitt Optimal) | Wilkinson, Matthew (Pruitt Optimal) | Buckner, Jason (Pruitt Optimal)
A novel drilling solution, ‘Constant Bottomhole Pressure (CBHP) Managed Pressure Drilling (MPD) assisted Casing Drilling operation’, was designed, planned and successfully executed for different operators on multiple directional wells in North America. These wells were otherwise not drillable either conventionally or with CBHP MPD using conventional drillpipe-BHA; and over the last few decades several operators tried and failed to reach the Target Depth (TD) on multiple occasions when drilling some of these formations.
One operator drilled in formations prone to severe faulting/fracturing and with very high permeability, while a different operator drilled through multiple weak zones interbedded with over-pressured and highly conductive regions. Both scenarios resulted in similar issues with fluid displacement, tripping/surge and swab, kicks and losses, running casing and cementing. The generic CBHP MPD solution with a conventional drillpipe-BHA even with ‘Anchor Point’ CBHP MPD and its variations was not successful in either of these scenarios in drilling to the TD.
As demonstrated using case histories, the success in these projects was a result of combining two technologies - ‘CBHP MPD’ and ‘Casing Drilling’. Pre-planning, understanding formation constraints, training, and having knowledgeable and experienced people involved, enabled safe and successful execution of CBHP MPD assisted Casing Drilling on these projects and helped CBHP MPD develop and reach new horizons.
Automatic and remote operated drilling chokes have been in the petroleum industry for a very long time. Managed Pressure Drilling (MPD) operations have been using these chokes since ±2006 and prior to that Underbalanced Drilling (UBD) operation have been using them for decades. The main control or actuation of these drilling chokes is achieved by adapting standard API-16C hydraulic or electric actuated worm gear drive actuators. These methods of actuation however have limitations related to ‘Response Time’ and ‘Equipment Failure’, making these actuators less desirable for MPD applications.
An advanced method of actuation using ‘Electro Servo Actuator’ is presented as an alternative to alleviate these challenges. These electro servo actuators are designed from the outset considering the requirements of MPD Choke operations, and are optimized to provide precise control of chokes along with a reduction in the number of potential failure points.
During extensive laboratory testing, required as a quality standard for our MPD choke’s factory acceptance program, these actuators provided very accurate and responsive pressure control to quick changes in pressure demands based on variations in both set point and flow. Furthermore, the initial field testing of the actuator in the MPD field operations demonstrated the same precise and accurate pressure control tracking, along with better performance at ‘lower flowrates’ when compared to worm gear driven chokes. Full-scale field application on over 20 different projects across North America, including a wide range of severe weather conditions, exceeded the expectations and results from initial testing.
In conclusion, the use of this new ‘Electro Servo Actuator’ technology greatly increases the precise control of drilling chokes very crucial for all MPD applications. This technology reduces the potential failure points in the actuators. It enhances the uptime of the actuator and its life cycle, thereby minimizing the need for routine maintenance. Its smaller size and design enables development of more compact MPD chokes and equipment.
Fully automated Managed Pressure Drilling (MPD), as a technology and oilfield service, has been evolving in capability since approximately 2005. Here we look at the application of downstream advance technologies for upstream operation optimization, via increased automation and the benefits this can bring to MPD systems.
The tools, standards and processes already developed and field proven in other downstream industries are readily available and applicable for upstream operation optimization, standard compliances, risk management and reduction. Utilization of smart instrumentation with real-time diagnostics, multi-sensor voting system, large diaphragm seals transducers, auto tracking pressure relief valve control and adaptive self-tuning surface back pressure (SBP) control deliver enhanced capabilities and functionality to improve not only the control of the well but the overall system inherent safety.
The Bergermeer Rotliegend sandstone reservoir has been depleted by production. This has substantially reduced reservoir pore pressure and well deliverability. Pressure depletion has been accompanied by a decrease in minimum in-situ stress, resulting in a substantially sub-hydrostatic drilling fluid density required to enable drilling. As a result, Managed Pressure Drilling (MPD) using two-phase fluid has been chosen as the
enabling technology for drilling and completing initial wells for the Bergermeer Gas Storage Project. MPD for the Bergermeer wells is defined as the use of two-phase flow drilling fluid including nitrogen injection via a tieback casing to maintain bottom hole pressure below the anticipated reservoir minimum in-situ stress at or near hole depth. Using MPD technology in the Bergermeer Gas Storage Project will enable drilling the planned boreholes without exceeding minimum in-situ stress, minimizing the risk of differential sticking and drilling fluid losses if natural fractures are present. Reservoir pressure in the Rotliegendes reservoir was originally 238 bar (3451 psi) at 2100 m (6890 ft) subsea. By mid-2009, gas reinjection was started to bring the reservoir up to an operating pressure of 120 to 180 bar for gas storage operations. By May 2013, when the first of the new gas storage wells in the Bergermeer reservoir was drilled, the formation pressure had been brought up to 81 bar. Due to permitting restrictions, it was not possible to drill a test/pilot well before drillingthe first gas injection/production wells to physically determine formation rock strength. Therefore, a decision was made to drill into the 81-bar reservoir with a target BHP of 117 to 127 bar; this equated to an ECD of 0.57 to 0.63 SG. Dynamic formation integrity tests were performed to determine formation rock strength in a controlled manner using two-phase MPD techniques at predetermined depths in the reservoir. TAQA drilled two wells during May and June 2013, one S shaped vertical well and one horizontal well into the two depleted formations. This was achieved maintaining a constant BHP within the predetermined window using MPD with gasified fluid; in fact it was possible to drill the wells with a very stable BHP with a 0.6SG ECD. For the TAQA Bergermeer Gas Storage project, significant planning into the overall system design, equipment selection, techniques, procedures, and training lead to an operation where precise control of the annular pressure profile was achieved and maintained throughout the operation.