Reservoir analysis during underbalanced (UB) drilling cuts costs and yields increases in both production and reserves, says Halliburton's Underbalanced Applications (UBA) group. An integrated delivery of data acquisition plus a truly safe and dependable program bears out at BP's Sajaa field in Sharjah - a two-year contract extension was granted in March.
Underbalanced (UB) Drilling is becoming an established wellsite technology, according to Ron Hyden, Global BD/Marketing Manager for UBA at Halliburton. Its ability to increase reserves, improve recovery, accelerate penetration rates and reduce formation damage has been clearly demonstrated. It can also reduce problems such as differential sticking and all those tools lost downhole.
In UB drilling the drilling fluid properties and the wellhead pressure are controlled so that a targeted bottomhole pressure is maintained, thereby allowing for continuous underbalance throughout. So a continuous production stream is maintained while drilling takes place.
The US energy technology company concedes that UB drilling costs more on a day rate basis than conventional overbalanced method. More planning is needed, and the process requires the pressure in the bore to be kept lower than the pore pressures of the formations passed through. Nevertheless experience shows that the process can more than return whatever extra costs are incurred by boosting output and cumulative recovery, all in complete safety and in an environmentally friendly way.
So UB drilling is being increasingly used in problem wells such as those penetrating depleted or under-pressured formations, fractured and fluid-sensitive materials, tight-gas sands, and in horizontal wells, too - all minimising the potential damage to the yielding reservoir.
Halliburton's UBA group has introduced a new Real-Time Reservoir Evaluation (RTRE) service to augment this new profit-boosting technology. RTRE integrates fit-for-purpose surface and downhole equipment with advanced data management and analysis techniques and bore/reservoir modelling - remotely if required - to allow resource characterisation whilst actually doing the drilling at the site.
'Planning a UB well or drilling campaign well before initiation of drilling activities and then rigorously adhering to the systems, procedures and techniques specified in the project management plan helps ensure that complex subsurface settings can be drilled underbalanced safely and without damaging weak geologic zones, Hyden explains.
Using their own specially-developed software the UBA group provides complete project management services including such tasks as hazard identification and operability assessments, risk analysis, site/rig inspections, procurement, complete equipment drawings and process flow diagrams, wellbore modelling and actual construction. Halliburton's INSITE database (from Sperry-Sun, a data acquisition platform) provides a reliable way of monitoring the progress of a UB well while the drilling takes place. RTRE provides an excellent testing-while-drilling capability that can be interpreted remotely and simultaneously in terms of such parameters as permeability and reservoir pressure. This allows the experts, wherever they are in Abu Dhabi or Aberdeen, to adjust the drilling programme as it actually takes place - which often allows unexpected reserves to be tapped. So economic production can be started earlier and resource recovery is maximised.
For three years Halliburton has been drilling and completing more than 30 Class 4/5 wells in UB mode without incident, with the RTRE process being applied to eight of these. Production rates at several sites have exceeded expectation ten-fold, and several times gas has been produced satisfactorily at more than 40mn scfd while UB drilling was actually taking place.
'This kind of success can reduce finding and development costs more than any other single factor," Hyden maintains. "Soon this process will be known as a disruptive technology that renders conventional well testing and reservoir evaluation redundant in many cases, altering the conventional work flow while enhancing the safety and effectiveness of UB drilling, and reducing the time required to obtain accurate reservoir data."
So UB drilling offers cost-cutting solutions for operational problems arising from reservoirs with low formation pressures, areas that experience excessive lost circulation, stuck pipe and lost-downhole incidents, low penetration rates and short drill-bit life. It also prevents formation damage in a significant way. So production costs are reduced and cash flow increased, excellent reasons for making UB drilling the choice for developing a new underground asset.
Hyden says, "UB drilling is much more than putting together a bunch of specialty designed equipment. Our reservoir description, well construction and project management skills and technologies are all brought together for an optimal UB programme that delivers value...you get the total solution.
"Our goal is to maximise reservoir performance without jeopardising safety or the environment. In 60 per cent of the projects we've project managed during the last two years, the operators had to go back and adjust their recoverable reserves estimate upwards."
The US company's sophisticated and compact four-phased, closed-loop separator technology provides on-site solids management systems for handling drill cuttings as well as the oil, water, gas and mud that routinely get ejected. Its patented mechanically activated Quick-Trip valve, available in sizes up to 9 5/8-in, provides reliable well control down the hole during tripping and while running the completion operations.
And Landmark Consulting & Services group complements this operational expertise by adding in-depth understanding of the emerging reservoir parameters. The project team combines reservoir engineering, geology, drilling, completion and product expertise to create the very best integrated technology solution for any reservoir encountered.
Success in Sharjah
BP AMOCO SHARJAH has extended by two years its contract with Halliburton to provide underbalanced drilling services in the Sajaa Field. This capitalises on the safe, dependable and revenue-earning application of UB services already employed. The international major recently completed its 18th well here using this technology earlier this year.
A special consortium is now providing services for the extended Sharjah project, with the US energy group supplying its Four Phase Separation System. Using the technology described above well stream fluid returns are processed on site to optimise use and conform to the stringent environmental rules that apply in this Emirate. Hydrocarbon recovery entails the compression and re-injection of gas and the pumping of condensate into the production line. Once checked over the wastes are disposed of with great care on land.
Halliburton is using its SCAN3 and INSITE Data Acquisition & Management Systems to gather and process all data from the project and present them in a common format for interpretation wherever the international client chooses through the SCAN network system.
Says BP Sharjah's Randy Pruitt, drilling manager: "BP greatly appreciates Halliburton for the effort in the Sharjah UB CTD programme, which has helped BP Sharjah reach the six million man-hours, and six years, without a DAFWC lost-time incident."
"We are pleased that UB drilling is enabling them to outperform benchmark production values," counters Gary Godwin, vice president, Production Optimisation Division, Halliburton. "As the industry recognises the value of this reservoir-performance-centred approach, Halliburton looks forward to providing UBA services to a wider array of reservoirs such as fractured carbonates, reverse condensate drives, lower pressure maturing fields and others."
For more information visit www.halliburton.com
© Oil Review Middle East 2004
