Successful Use of Managed Pressure Drilling (MPD) to Counteract Loss Circulation and HP Gas Zones: A Case Study from Red Rock South Wapiti Field in Grande Prairie, Alberta, Canada
Authors: Malik Hassan. K. , Litwin Raymond. J. , Jones Bernard. C. 
Published: February 2011

Heavy Mud Weight (MW) to control HP gas and Loss Circulation zones at the same time is not something operators look forward to. COP's Red Rock field in South Wapiti, Alberta had been a victim of this combination which resulted in high operational costs primarily due to additional casing string, high MW and severe mud losses. On average, AFE's came at a minimum of 20% higher as anticipated bringing the drilling program of the area to being uneconomic.

A review of MPD technology with the team created a spark to look at improving performance in the area. A number of objectives were identified for this project which were later categorized as

Primary Objectives.

Drill to TD with reduced mud weights (MW) in a safe manner Set the intermediate casing on top of HP gas zones utilizing wellbore strengthening Drill ahead into HP zones without any massive mud losses Bring the cost of the wells down in order to save the drilling program of the area Eliminate the Intermediate Casing for a significant cost reduction in future wells

Secondary Objectives.

Conduct Real Time Formation Evaluation in some formations to verify their potential Increase ROP Cement the Intermediate Casing using a single stage method Assess and evaluate the benefits of a new technology Rig crew training and changes in HSE concepts for an MPD operation

A dedicated Engineering team was formed who worked on data collection, research of the area, drilling practices and well engineering. This team was supported by COP's experienced Operations team. A great deal of up front discussion and work was done in planning this project to ensure success. Several well design scenarios were looked at the very initial phase of project, out of which the best design in terms of well engineering, well control, area's known risks and HSE was chosen. During this process COP's engineering team introduced "Fountain Chart Method" which uniquely identifies operating envelope of an MPD operation using optimum mud weights

From the initial design the specifications of the MPD equipment were decided upon. A meticulous work was conducted on Process Flow Diagrams (PFDs) of which Well Control was of pivotal importance. Special training was assigned to the rig crew detailing goals of the project, working of MPD equipment and communication skills in the presence of another vendor on site. The HSE alert level was heightened due to the sensitivity of the project and extra emphasis was given on safety meetings highlighting high pressure lines, communication skills and drilling with wellhead pressure on surface.

Promising results were seen in a four well campaign which not only brought the cost of the wells down but also made the wells more economic. The lower cost of the wells were a result of an improved ROP in some sections and the replacement of a full intermediate string coupled with a liner with only a single production casing string from surface to TD. An added benefit is the technology helped in studying the formations at low MW which were previously masked due to heavy MWs. Utilizing Wellbore Strengthening (WBS) was also a key in establishing integrity of weaker zones up hole. This in turn, gave a better window of applying surface choke pressures using MPD auto choke system.

The success of these wells has led to further implementation in the Canadian BU. As a result, a screening tool was developed for internal review of candidates/fields that may benefit from MPD, UBD or any other unconventional style of drilling (such as Air, Aerated Mud or Foam etc). A process is underway in assessing the benefits of these technologies in COP's drilling portfolio and ways are being looked at in making an effective process for implementing these sorts of high profile projects in the future