Recent developments in permanent downhole monitoring provide accurate and stable measurements even in extreme high pressure/high temperature reservoir conditions. The integration of multiple measurements as they happen allows operators to make field decisions for production and reservoir management.
‘Permanent’ downhole well monitoring is nothing new, as pressure gauges have been installed in wells since the 1960s. Just like commercial communication and remote sensing satellites that are deployed in a very harsh environment and are usually inaccessible for repair, well monitoring systems must be engineered to last. The technology has grown from just monitoring downhole pressures to integrating multiple measurement solutions for activities such as flow profiling, fracture monitoring, production surveillance, and thermal profiling. These data are sent to thesurface using a downhole cable and processed through a scalable datamanagement platform. Simply put, this allows the operator, through integrated software, to simultaneously visualise dynamic, multi-parameter data under changing well conditions.
From Standard to Extreme Conditions
One technology developed to address these issues is Weatherford’s OmniWell™, a unified family of pressure, thermal, flow and seismic products that provide an accurate view of well conditions. These systems have now been installed worldwide in reservoir conditions that range from conventional to extreme. All types of well and development activity can be monitored, including both electronic and optical sensing technologies for conventional and unconventional oil and gas fields. Past monitoring systems relying only on electronic pressure/temperature (P/T) sensors were found to be not dependable under extreme conditions such as high temperature (HT), high temperature/high pressure (HT/HP), high vibration/shock or complex deviated wells. Bearing this in mind, Weatherford International has developed optic sensing technology as part of the OmniWell Production and Reservoir Monitoring solution. This has proven reliable in the most extreme temperature and pressure downhole environments, including maximum reach (MRC) smart wells, multilateral horizontal wells, ultra high temperature/high pressure deep gas wells, and ultra- high temperature heavy oil steam wells.
These systems are providing added value in the form of key continuous realtime production and reservoir data to the Middle East and North African (MENA) countries, whose economies depend on the hydrocarbon industries despite recent efforts to diversify. The MENA region holds more than half of the world’s proven oil reserves and a significant percentage of the world’s gas reserves (see How Much Oil in the Middle East?, page 42). With recent developments in tight and unconventional hydrocarbons, it has become more important for operators in this area to find new resources, cut costs and optimise production for their existing resources.
New oil and gas projects for this region total in the hundreds, and the OmniWell monitoring solution is being used in 11 MENA countries with fibre optic monitoring being deployed in extreme downhole conditions in Kuwait, Oman, Saudi Arabia and Algeria. The technology has proven reliable and useful in understanding the structural, dynamic, and geological behaviour of the region’s complex reservoirs.
Success in North Kuwait
Relying on over 19 years of experience with optical gauges deployed in oil and gas wells, with thousands of sensors, and over a spectrum ranging from conventional to some of the most challenging downhole environments, Weatherford and the Kuwait Oil Company put their fibre optic sensor technology through a pilot test programme in 2011. They selected a deep, HT/HP gas well in the Raudhatain Field in North Kuwait.
Ridha Abid, Weatherford International Regional Product Line Manager, had this to say about the pilot project: “The purpose of this pilot programme was to test our fibre optic sensor technology in a deep, HT/HP gas well. Reliability of electronic systems used under these conditions tends to fall off dramatically with increasing temperatures over time. Optical systems have numerous advantages over electronic systems in that there are no electronics downhole and no moving parts. They can withstand continuous, combined high temperature, pressure and vibration downhole from flowing gas wells and can work at temperatures exceeding 230°C and pressures exceeding 20,000 psi. Optical systems can also withstand the high vibration levels associated with gas wells. Add to these advantages a longer reach capable of tens of kilometres of cable versus the shorter distances available for quartz gauge systems, and it becomes no contest between the technologies.”
For the pilot project, an optical P/T gauge rated to 175°C and 20,000 psi was installed in the well above the production packer at a depth of 4,115m in a 4,785m wellbore. The gauges were to provide continuous measurement of tubing pressure and temperature. The equipment was subject to downhole temperatures up to 138°C and pressures up to 9,500 psi during the test.
“We consider the all-optical approach for monitoring these extreme gas wells attractive,” Ridha Abid continues. “The system installed in Kuwait is a secondgeneration optical P/T gauge that is the product of many years of industry optical experience. The first optical P/T gauge was installed in the Gulf of Mexico in 2000 to monitor long-term reservoir pressure and is still operational. This technology is based on very simple concepts: generating light rays from a light source, transmitting the rays through the fibre to the optical sensor and receiving back the reflected light by a receiver. The receiver decodes the information riding the light waves.
“The OmniWell fibre optic pressure and temperature gauges installed in 2011 have survived the HT/HP downhole environment and are continuously providing reliable, real-time pressure and temperature data to operations personnel on site and to engineers in the Kuwait Oil Company office. The data have proven valuable in monitoring the well intervention and production programmes, determining initial reservoir pressure, managing well drawdown, diagnosing completion problems, building wellbore hydraulics, inflow performance models, and providing pressure build-up data – all without the need for well interventions and the resulting loss in production volume. In addition, a much better understanding of the structural, dynamic, and geological behaviour of these complex reservoirs has been obtained. To maximise the benefit from permanent downhole gauges, it is being recommended that such devices be installed in more future wells of North Kuwait fields.”
More Than ‘Just’ New Tools
“Weatherford has not only developed a fibre optic system that can operate reliably in just about any downhole environment, we are also bringing an approach that simplifies and unifies integration and workflows for reservoir solutions for all well types in today’s broad range of production environments,” says Tad Bostick, Vice President of Reservoir Monitoring for Weatherford. “This is a shift from the tool-based or fragmented data collection approach to a more unified solution where various streams of critical data are transferred to an operator from multiple downhole sources. This unified system allows the operator to make better production and asset management decisions.”
Along with the successful testing programme in North Kuwait, Weatherford’s optical systems are being installed across the Middle East and North Africa. In Oman, for example, this monitoring system has been installed in HT/HP gas wells to gather data during hydraulic fracturing operations. The P/T gauges were manufactured specifically to withstand the pressures generated during the hydraulic fracturing process. In addition, their surface equipment was solar powered in the remote location. The client was provided with real-time monitoring that allows the optimisation of hydraulic fracture operations. The accurate and stable P/T data from the appraisal wells has enabled management to fully evaluate the field.
The real-time data collected across the Middle East and North Africa is helping keep the region in the forefront of hydrocarbon production by providing management with the means to maximise field development while lowering overall costs.