Tangen, Geir Ivan (Lundin Norway AS) | Smaaskjaer, Geir (Lundin Norway AS) | Bergseth, Einar (Lundin Norway AS) | Clark, Andy (Lundin Norway AS) | Fossli, Børre (Enhanced Drilling AS) | Claudey, Eric (Enhanced Drilling AS) | Qiang, Zhizhuang (Enhanced Drilling AS)
In 2015, while coring in the carbonate reservoir in the second appraisal well on an oil and gas discovery in the Barents Sea (386 m water depth), the drill string fell 2 meters and a total mud loss was experienced leading to a well control incident. As a result, since 2016, the operator has introduced and used the Controlled Mud Level (CML) system. To date this system has been used on seven wells including two further appraisal wells on the same field and five exploration wells in the area.
In 2017 it was decided to drill a horizontal well in the same carbonate reservoir and to perform an extended production test in close proximity to the original loss well. Since it is not possible to predict where large voids (karsts) and natural fractures could be encountered, contingency to handle high losses, had to be implemented for the horizontal well. During the well planning, further risk reducing measures were implemented, including the use of wired drill pipe to improve the management of the wellbore pressure profile. This paper describes the planning processes leading up to the operation and the highlights of the operation itself together with the lessons learned. It elaborates on how wired pipe, used in combination with the CML system, added value to the operation. It shows how it was possible to drill the reservoir section with a low overbalance while managing severe losses associated with open karsts and natural fractures and still maintaining the fluid barrier. Despite the severe losses encountered it was possible to safely drill and complete the well without any well control event by use of the CML system.
This paper presents design, testing, installation, and lessons learned with the world's first completely integrated managed pressure drilling (MPD) control system on a deepwater drilling rig. While previous MPD installations have included driller-operated systems, they all include additional human machine interfaces (HMI) and standalone control network components with limited use of rig data and limited to no interfaces to other critical drilling machines on the drilling rig. For the installation described in this paper, all MPD control functions were permanently installed on the main drilling control network of the drilling unit, providing direct access to high speed data from other drilling machines that influence the wellbore pressure. This includes the rig's mud pumps, top drive, and drawworks. Moreover, the MPD control system has the ability to actively control the drilling machines, thereby optimizing performance through coordinated control of mud pump, top drive, and MPD chokes during drilling and connections.
To safely plan and execute MPD Influx Control operations, the limits of the primary barrier envelope must be communicated and understood. These safe operating limits have historically been represented with an MPD Operations Matrix. More recently, the development of the Influx Management Envelope (IME) has provided a means of communicating the primary barrier limits with improved accuracy and clarity. However, the generation of the IME currently requires performing a series of complex well control simulations with specialist engineering support. Because drilling operations are dynamic in nature, a practical method to generate the IME boundaries at the wellsite is required so that changes to mud weight, flowrate, surface and bottom hole circulating temperatures, trajectory, and bit depth can be accounted for, and the IME kept up to date.
This paper describes the development of a novel tool to quickly and automatically generate IMEs at the wellsite without the need for sophisticated modelling software and specialist personnel. The single bubble derivation that was originally presented by Culen et al was analysed further to obtain a more accurate and explicit relationship rather than an implicit one, which forms the basis for the calculations. The IME can be updated based on any well parameter changes, which allows field engineers to maintain an up to date and accurate IME throughout MPD operations.
The last several years has seen an increasing trend toward more depleted reservoirs and more challenging wells with tighter mudweight windows. Managed Pressure Drilling has been employed in these challenging well conditions, however industry take up has been slow for a number of reasons including technical, economic and deployment related. Those wells that have utilized Managed Pressure Drilling have tended to focus on the drilling related aspects of well construction. However, other areas of well construction such as casing and liner running and cementing and completion installation are equally and in some cases even more technically challenging. One area that has potentially hindered the uptake of Managed Pressure Drilling is that in general, and in particular in the well construction operations outside of on bottom drilling there has been no access to real-time downhole data. In particular this is related to real-time pressure data. Whilst cementing, displacing or completing then multiple fluid types and densities may be circulating both inside and outside the drillpipe, leading to significant challenges in simulations and models derived from surface data. To overcome this a new acoustic telemetry and measurement network is being deployed in depleted reservoir and managed pressure drilling operations to provide real-time downhole and along string measurements of pressures, temperatures and weights. Real-time data case histories will be shown from the Gulf of Mexico and the North Sea illustrating how this is being used to drive real-time decisions during drilling, cementing and completion installation operations in tight margin windows, depleted reservoir conditions and under managed pressure drilling operations.
Nitrogen Cap Drilling (NCD) is a technique developed by Tengizchevroil (TCO) that enables drilling a highly fractured reservoir under conditions where more conventional pressurized mud cap drilling techniques are not viable. NCD is an extension of the closed hole circulating drilling (CHCD) technique (Ref SPE Paper # 79850) previously developed and used extensively by TCO for drilling a highly fractured carbonate reservoir where severe loss circulation is encountered and incurable.
CHCD is a pressurized mud cap drilling technique that relies on the ability to fill the well with a fluid density lighter than the reservoir pressure gradient in order to maintain communication with the reservoir pressure. Once the reservoir pressure gradient drops below the density of the lightest fluid available, the well will no longer support a full column of fluid to surface and an alternate drilling method must be employed.
TCO has developed NCD as a response to this operating reality in the Tengiz field. The NCD technique involves filling the annulus with a heavier than reservoir pressure gradient fluid once severe lost returns are encountered. The annulus fluid level does not reach the surface, and the resulting air gap is pressurized with nitrogen gas. This nitrogen "cap" is contained under the Rotating Control Device (RCD) which allows for maintaining pressure communication with the formation. Well status is continuously monitored by tracking the wellhead pressure and measuring the annulus fluid level. The bottom hole pressure is balanced by manipulating the composition of the annular fluid column and controlling the wellhead pressure.
In 2017, TCO conducted successful field trials and demonstrated that NCD is a viable technique to enable the continuation of the low reservoir pressure drilling program in Tengiz. TCO has since adopted NCD as the standard technique in wells where CHCD is not technically viable or operationally preferable. This paper will describe NCD technique development, equipment, procedures, operational implementation, and key learnings to date.
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.
Fernandes, Andre Alonso (Petrobras) | Vanni, Guilherme Siqueira (Petrobras) | Martinello, Isac Alexandre (Petrobras) | Terra, Felipe de Souza (Petrobras) | Sales, Ivan Mendes (Petrobras) | Guedes, Jonas (Petrobras) | Vasconcelos, Kelliton da Silva (Petrobras)
Manage Pressure Drilling is not a new technology, but the transition from land operation to floaters is still recent. This created a situation where drilling contractors and operators are still learning what the true capabilities of the technology are.
MPD technology adoption on floaters can be divide it in 3 different phases: Use for Early Kick Detection and wellbore stability improvement; Introduction of Hydrostatically Underbalanced fluid; Influx circulation through the MPD system;
Use for Early Kick Detection and wellbore stability improvement;
Introduction of Hydrostatically Underbalanced fluid;
Influx circulation through the MPD system;
In the first phase most of the procedures and barrier concepts stay untouched.
After eliminating initial skepticism, second phase commences. Hydrostatic pressure exerted by the fluid is inferior to the formation pressure. Primary barrier concept alters. The technology can be applied to drill wells with narrow operational windows, unviable conventionally.
Finally, third phase starts with very limited volumes being allowed to be circulated through the MPD system. After first successful influx circulations through the MPD system, increased volumes may be encouraged to be circulated through the primary barrier.
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.
Drilling in high pressure high temperature (HPHT) deep gas reservoirs, with multiple shallow different pressure horizons, requires special techniques which include application of Managed Pressure Drilling (MPD), revising casing setting depths, improving casing strength, and refining mud design. This paper focuses on application of MPD in HPHT gas wells and also describes briefly other techniques which can improve drilling performance and reduce nonproductive time.
CML (Controlled Mud Level) is a dual gradient type of Managed Pressure Drilling (MPD). The CML system was developed and implemented on the Troll field to allow for reducing the annular pressures acting on the wellbore during drilling, thus allowing drilling areas weakened by faults and fractures and longer horizontal sections in the depleted normal pressured reservoirs. This paper will present a short introduction to the Troll field, a description of the system utilized, a summary of the rig integration, operations and experiences with the CML system on Troll.