A few horizontal wells were drilled in Kuwait, heavy oil field, as a part of cold production testing. Various workover interventions were performed on these wells. However, some of the wells showed sharp production decline and were producing below expectations. It was suspected that formation damage may have occurred in these ultra-low reservoir pressure wellbores due to the overbalance of the fluids used during interventions.
Concentric coiled tubing (CCT) technology comprising of a downhole jet pump, was recently employed for the first time in Kuwait and was determined to be an effective method to clean the horizontal sections and investigate the reasons for the production problems. The single phase cleanout fluid is circulated down the inner string to power the jet pump, creating a localized drawdown that vacuums the formation solids or fluids out of the wellbore and the combined sand/fluid stream returns via the CCT annulus. The multiple operating modes provided the benefit of cleaning and treating the wellbore in the same run.
This specialized system was successfully utilized to remove sand, evaluate the formation damage and enhance production; meeting all objectives in a single well intervention. Pressure and temperature gauges run below the tool on two wells recorded bottomhole pressure of only 150 psi. Post-production results has pushed the boundaries of the well interventions in heavy oil field in Kuwait and has unlocked several wellbore cleanout and formation damage evaluation opportunities using the CCT technology.
This paper reviews the benefits of the concentric coiled tubing technology and provides a comprehensive case study of the first three horizontal wells. The analysis of the sand and fluid influx profiles obtained during the vacuuming process assisted in to evaluating well production provided crucial data in formulating a management strategy.
Coiled Tubing deployed Electrical Submersible Pumps (ESPs) have had a very short history in the oil and gas industry. The idea of installing a pump using coiled tubing was developed more than a decade ago which would allow the possibility of rigless operations and reduce the time for deployment/retrieval of the completion under “live-well” conditions. However, the initial attempts to define their economics were limited to comparing operational costs based on equipment and services, without considering the long term performance and gains over the life of the installation.
A new concept of power cable consisting of 3 mono-conductors has been developed in the past 2 years for deploying ESPs that eliminates the need for spooling and banding at the wellhead. The project has been a strategic development for ESP alternative deployment methods that would eliminate the need to move a work over rig on location to replace/service an ESP, making it more cost effective. A customer in Saudi Arabia has chosen the path of performing an initial recompletion of the well with this system with the benefits of the alternate deployment method during the periodic ESP replacements for resizing and wear out.
This paper outlines the details of the new cable deployed ESP system and the extensive considerations given to the deployment process to ensure safe and successful installation of the ESPs.
Electrical Submersible Pumping Systems (ESPs) are becoming an increasingly important artificial lift method. As reservoir pressures deplete and water cuts increase, the need for high volumes of production remains, and this technology fills a critical need. One of the key challenges faced by operators is how to most efficiently deploy and maintain these systems. Deploying ESP's on conventional jointed pipe is adequate for low pressure onshore wells but higher pressure or even naturally flowing wells, especially offshore, can be problematic. In many cases, drilling rigs are being utilized for these ESP installations, which is both costly and an inefficient use of drilling systems.
An operator needed to perform wellbore intervention on four low-bottomhole-pressure offshore wells in Malaysia. High sand production was consistent in all the wells, precluding access to the producing zones in the lower completion. The wells had been shut in since 2011, and previous cleanouts using conventional coiled tubing (CT) and nitrogen had been unsuccessful.
The job had to be performed from a work barge in a catenary style, meaning that the injector head, blowout preventers, and power pack were on the platform, but all were operated from a barge. The advanced wireless catenary unit made it possible to complete the operation with only the CT and three flexible lines connecting the barge and the vessel. Due to the nature of the concentric coiled tubing (CCT)—designed to flow returns back to surface—all returns had to be routed away from the platform and onto the barge.
After an analysis and planning session, the operator and the service provider decided to use a CCT cleanout system with a switchable jet-pump designed to remove solids and liquids from ultralow pressure wellbores that are not treatable with standard circulating methods. The operational plan also called for building a specialized CT connector that would enable conventional operations, such as fishing and sleeve manipulation with CCT.
This was the first time that vacuuming technology and catenary CCT were used together to perform a cleanout operation. The results were impressive as extensive amount of sand was removed from the wellbores to surpass target production by 185%. This paper will focus on a campaign in the South Furious field of Sabah, Malaysia in which both the logistic and operational challenges were successfully overcome with 112 days of incident free operations.
Sand Jet Perforation (SJP) is a process which uses a high velocity jet of abrasive sand laden fluid to cut through the casing, cement and into the formation jetting pressure and cutting time can be varied to achieve maximum penetration.
The process begins by using Coiled Tubing to convey, accurately position and operate the sand jet perforating tool with integral casing collar locator (CCL). The sand jetting assembly perforates the zone; the CT is moved uphole to allow an optimum fracture treatment to be pumped down the casing/CT annulus. Based on the difference in depth of the perforation interval between the zones to be fractured, the underflush volume for fracturing treatment is calculated to place a sand plug in order to isolate the zone at the end of the treatment. If this is not sufficient, the sand used for perforating the next zone is allowed to settle to form additional plug height. An added advantage of using this technique includes washing off the extra sand (if any) using Coiled Tubing in the same run, which leads to saving significant amount of time and eliminates the need of setting up expensive packers to achieve zonal isolation in multi-zone wells.
With conventional wireline perforations, about 12 to 15 zones were usually fractured in a month in the Raniganj Coal Bed Methane (CBM) Block, India. The application of the above technology, made it possible to fracture more than 38 zones in a month. The process ensured that each zone received a positive zonal isolation and optimized fracturing treatment leading to cost effective and quality fracturing treatments.
This paper highlights the sand jetting perforation process for achieving maximum penetration, advantages of the technique for fracturing in CBM wells and the planning involved placing sand plugs for achieving optimized and economic stimulation treatment.
Improved Oil Recovery (IOR), techniques offer prospects that enhance the displacement of oil from the reservoir, ultimately producing 30 to 60 percent, or more, of the reservoir's original oil in place. The most important criteria in IOR- Surfactant Flooding is to determine if the interfacial tension (IFT) can be reduced enough to produce incremental oil.
One of the key recovery problems in oil-wet reservoir is overcoming the surface tension forces that tend to bind the oil to the rock. In water wet reservoirs, surface tension forces act to create bubbles of oil, which can block pore passages as the bubble resists movement in the increased surface area associated with squeezing through the passages. These surface tension forces are the primary reason why reservoirs become increasingly impermeable to oil, relative to water, as the water saturation increases.
Ferrofluids are a special category of smart nano-materials, in particular magnetically controllable nanofluids. The ferromagnetic nano-particles are coated with a surfactant to prevent their agglomeration. As a result of their composition, Ferrofluids possess a unique combination of fluidity and the capability to interact with a magnetic field. The addition of a surfactant will greatly reduce the Interfacial Tension and in water-wet reservoirs, where oil globules are formed, ferrofluid shatters it. Also, as ferrofluid comes in contact with the reservoir fluid, it interacts with the crude in the reservoir & due to the presence of dipole moment, the reservoir fluid molecules align, thus reducing the resistance to the flow.
To sum up, reduction in Interfacial tension, thus reducing resistance to the flow, can be easily achieved by making use of Ferrofluid-enhanced surfactant. Oil can be made even more polar using Ferrofluid which will act as a better solvent for the surfactant.
A ferrofluid (FF) is a type of smart fluid. It is a suspension of nano-sized magnetic particles in a carrier fluid, usually a type of oil, or water. When subjected to a magnetic field, the fluid greatly increases its apparent viscosity, to the point of becoming a viscoelastic solid. Importantly, the yield stress of the fluid when in its active ("on") state can be controlled very accurately by varying the magnetic field intensity. Although the name may suggest otherwise, ferrofluids do not display ferromagnetism, since they do not retain magnetization in the absence of an externally applied field. In fact, ferrofluids display (bulk-scale) paramagnetism, and are often referred as being "superparamagnetic" due to their large magnetic susceptibility. Permanently magnetized fluids are difficult to create at present.