Drilling & Production

The drillship Stena Forth is due to start a three-well campaign for Tullow Oil offshore Ghana in October. (Image courtesy Stena Drilling)

The drillship Maersk Venturer, which began operations in March, later than planned, has to date drilled a production well in the Ntomme area of the TEN field and two producers at Jubilee.

The rig is now undergoing preparations for well completions, and the Ntomme well should come onstream this month. It will then complete the two Jubilee producers and a previously drilled water injector on the field, while the Stena Forth focuses initially on drilling new wells.

First-half output from Jubilee will likely be a little below expectations due to downtime caused by work on the gas compression system.

However, this activity has had the beneficial effect of raising the vessel’s gas compression capacity and as new wells come online, oil production should rise. The Jubilee FPSO has regularly delivered around 100,000 b/d from existing wells since the works were carried out.

The FPSO Kwame Nkrumah was shut down for two periods earlier this year in preparation for planned remediation work to stabilize the turret bearing, allowing the vessel to operate long term in spread-moored mode.

Toward the end of the year there will be a final shutdown to rotate the FPSO to its permanent heading and install the final spread mooring anchoring system.

At TEN, first-half production is set to average around 65,100 b/d. By year-end, with the first two Ntomme wells onstream, output should climb to around 80,000 b/d.

Gas from the TEN fields was supplied to the Ghana National Gas Co. to replace supplies from Jubilee during the FPSO shutdowns. Gas sales from TEN should begin in earnest in July.

Elsewhere off West Africa, Tullow says it expects to start drilling the potentially high-impact Cormorant prospect in the PEL37 license off Namibia, using the Ocean Rig Poseidon.

Off Mauritania, a 9,000-sq km (3,475-sq mi) 3D seismic survey is complete across block C-18. Interpretation of this and the block C-3 survey, recorded last year, is under way to identify future drilling candidates.

Petrofac to provide well management services offshore New Zealand

Tamarind Taranaki has contracted Petrofac’s Engineering and Production Services division to provide well project management services for the Tui Phase 3 drilling project offshore New Zealand’s North Island.

Petrofac’s team will undertake detailed well design and planning, subsea support, HSE management, and logistics for the Tui oilfields west of Taranaki.

Tamarind acquired ownership of the Tui oilfields earlier this year. The Phase 3 drilling project is part of the company’s wider strategy to prolong the life of the Tui field beyond 2019.

Colin Finnegan, well engineering regional director, Petrofac Engineering and Production Services, said: “We will work closely with our new client to deliver a safe and cost-efficient drilling program that maximizes value and ultimately extends field life.”

Halliburton wins well construction services contract offshore Norway

OKEA AS and Halliburton have announced that they have signed a well construction services agreement to implement Halliburton Landmark’s full suite of software in the iEnergy cloud and field development planning services for all OKEA fields in the Norwegian continental shelf (NCS).

OKEA says that it is developing new marginal fields, and cost-efficiency is vital to ensure that the projects provide economic returns. After an open selection process, OKEA said that it chose Halliburton to support the company as it works to develop fields in the NCS more effectively.

Through detailed subsurface studies and scenario optimization, OKEA says that its goal is to establish an integrated service delivery model that will allow for the construction and service of wells throughout the fields’ lifecycle.

Rig measurement system improves kick detection

GEOLOG has introduced a rig measurement system to assist offshore well control.

According to the company, advanced flow meters are often installed on the mud return line to closely monitor drilling fluid in order to improve early kick detection capability.

On floating drilling rigs, however, heave movement affects the accuracy of critical return flow measurements. The heave effect leads to movement of the telescopic joint into the riser, displacing the drilling mud into the returns flowline.

These movements introduce variations in return flow that mask the true flow responses from the well, the company adds.

Its solution is an accelerometer, located at the center of gravity of the installation, continuously measuring the rig’s movement under the heave combined with a predictive algorithm.

The latter computes and compensates the flow variations induced by the telescopic joint’s ‘pump’ effect.

A self-tuning feature is designed to adapt to changes in heave height and period in real time, with no additional operator input needed.

According to GEOLOG, various major operators have used the system for deepwater drilling offshore West Africa, with one operator expanding its use to deepwater European/CIS operations.

The system is tuned and once the predictive system’s operating parameters have been acquired, GEOLOG says it can detect and measure the flow-out component caused by the rig’s heave movement in real time.

It then eliminates this from the flow-out measurement – already normalized for drill pipe displacement and changes in circulating parameters – to derive a true ‘Heave Compensated Flow-out’ measurement.

The system continues the tuning process, adapting to changes in heave height and period in real-time, facilitating detection of kicks and losses on floating rigs, and ruling out false alarms resulting from heave motion. •