Shell sets African record in expandable open hole technology

Shell Petroleum Development Company (SPDC) has successfully deployed the first Expandable Open Hole Clad (OHC) in the Africa region, to boost oil production in its operations and expand the frontiers of technological breakthrough.
To achieve this feat, a steel tubular was expanded by means hydraulic exertion while drilling an appraisal well Zarama-7 (a gas well). Subsequently the drainage interval of the objective gas-bearing reservoir points were exposed to flow integrity. Zarama-7 was spudded late last year but the Expandable Open Hole Clad technology deployment was achieved in early January, 2006.

While speaking on the development, Tunde Alabi, the Senior Wells Technology Specialist said OHC opens the door for effective utilisation of the solid expandable tubular technology in a number of upcoming wells. A key challenge in drilling wells where reservoirs are very close together is their effective isolation to prevent interferences so the measurement and management of flow rates and other vital life signs are as precise as possible.
In the case of Zarama-7, the drilling team was keen on getting the results right first time as these would guide future hydrocarbon exploration in the field.

With SPDC the conventional way of isolating production zones has been plugback cementation, a process where industrial cement is pumped into the reservoir. As it hardens, it isolates the producing zone.
Another method incorporates the utilisation of Swellable Elastomeric Packers. These are rubbers that contain special properties which make them inflate on contact with gas or oil or water. When deployed in a reservoir, they inflate to shut production zones. However, the SPDC team at Zarama-7 found these methods unsuitable and had to explore the OHC technology.

"The OHC was the only technique that met the functional requirement and enabled achievement of the well objectives. The cementing option held the potential hazard of impairing and damaging the target reservoir thereby mitigating its production potential. Plugback cementation had the advantage of reducing impairment and optimised data acquisition but the major drawbacks were the smaller production potential from reduced production hole size.”
"On the other hand, using Swellable Elastomeric Packers was easy and simple but over time, the ability of the rubbers to continue to maintaining sealing integrity was uncertain," Tunde explained.

In an ingenious approach, the team settled for the use of Expandable Open Hole Clad with the Swellable Packers.
"For the OHC deployment, we used a 7-5/8 tubular (made of steel) with special swellable elastomers applied to the exterior to ensure extra integrity. Through a special down hole cold-working process, the tubular was expanded against the intended formation in such a way to effectively create a seal and isolate it from the rest of the well. We were able to abandon and isolate the water-bearing S4.0 sand from the objective S3.0 gas reservoir.

The achievement ensured the integrity of production and acquisition of accurate data and readings. Zarama-7 has been tested to a production potential of 100 mm cf of gas per day. The drilling of the well is part of a campaign by SPDC to meet its gas supply commitment to NLNG.
Also speaking, Hans Flikkema, the outgoing Wells Manager and Thompson Ukomah, the Standards Expertise and Technology Team Leader commended the team for a job well done. They both noted that the achievement is a worthy extension of the successes already recorded in the area of Expanded Sand Screen Technology deployment in Nigeria.

Mr Valentine Emeh, the lead Well Operations East while speaking noted that the successes achieved so far could be attributed to effective team by Well Engineering, the Expandable Global Implementation Team, Opportunity Development Centre and the Land East Asset Team.
The Enventure GTan STV JV company is owned 86.5 % by Shell and 13.5 % by Halliburton, the contractor which provided the deployment service.