Corrosion in offshore well completions can lead to serious well integrity problems and costly workover operations. Although carbon steel is an ideal material for most completions, under certain conditions corrosion can attack and severely damage carbon steel equipment. Corrosion resistant alloys (CRA) are a good option but come with the considerable downside of very high cost. A relatively simple and cost effective approach to protect completion equipment against these corrosive elements is to line carbon steel completion tubulars with a non-metallic Glass Reinforced Epoxy (GRE). The GRE material properties provide excellent protection against a range of conditions including; highly corrosive fluids, erosive granular materials, Carbon dioxide (CO2), Hydrogen Sulfide (H2S) and acid treatments. The GRE lined Carbon steel is capable of combatting a range of corrosive environments in oil producers, water injectors / supply wells, including water with high concentration of total dissolved solids (TDS), chloride and sulfates and oil with high levels of H2S and CO2. The steel tubing is protected from these unforgiving ecosystems by lining the inside of the tubing with one continuous GRE tube. To secure the GRE lining and to increase the strength, a cement is pumped down the narrow annulus between the GRE lining and tubing internal wall. This procedure is relatively simple with the resultant GRE lined tubing having exactly the same tubing strength properties as the bare tubing. The primary method for detecting any well integrity problems with water injector wells are from determining high pressures in the tubing casing annulus (TCA). To date, all of the water injector wells installed with 7" GRE lined tubing have remained integral with no indication of any corrosion. Several of the oil producer and water supply wells that were lined with GRE have subsequently been worked over to replace faulty equipment; primarily electrical submersible pumps (ESP's). Encouragingly, the condition of the recovered GRE tubing had suffered no corrosion, scaling or other degradation benefiting from the GRE protection. The non-metallic GRE material is exceptionally robust with notable longevity and very resistant to any scale build-ups, leading to improved flow assurance. At the same time being tough enough to withstand any routine well intervention for logging, acid stimulation and other applications. The durable qualities and chemical characteristics of these non-metallic materials in downhole completions is likely to expand in the coming years, with increasing applications being found.
Summary Successful reservoir surveillance and production monitoring is a key component for effectively managing any field production strategy. For production logging in openhole horizontal extended reach wells (ERWs), the challenges are formidable and extensive; logging these extreme lengths in a cased hole would be difficult enough but is considerably exaggerated in the openhole condition. A coiled-tubing (CT) logging run in open hole must also contend with increased frictional forces, high dogleg severity, a quicker onset of helical buckling, and early lockup. The challenge of effectively logging these ERWs is further complicated by constraints in the completion where electrical submersible pumps (ESPs) are installed, including a 2.4-in. bypass section. Although hydraulically powered CT tractors already existed, a slim CT tractor with real-time logging capabilities was not available in the market. In partnership with a specialist CT tractor manufacturer, a slim logging CT tractor was designed and built to meet the exceptional demands of pulling the CT to target depth (TD). The tractor is 100% hydraulically powered, with no electrical power, allowing for uninterrupted logging during tractoring. The tractor is powered by the differential pressure from the bore of the CT to the wellbore and is operated by a preset pump rate from surface. Developed to improve the low coverage in openhole ERW logging jobs, the tractor underwent extensive factory testing before being deployed to the field. The tractor was rigged up on location with the production logging tool and run in hole (RIH). Once the CT locked up, the tractor was activated and pulled the coil to cover more than 90% of the openhole section, delivering a pulling force of up to 3,200 lbf. Real-time production logging was conducted simultaneously with the tractor activation; flowing and shut-in passes were completed to successfully capture the zonal inflow profile. Real-time logging with the tractor is logistically efficient and allows instantaneous decision making to repeat passes for improved data quality. The new slim logging tractor (SLT) is the world’s slimmest and most compact and is the first CT tractor of its kind to enable production logging operations in openhole horizontal ERWs. The importance of the ability to successfully log these ERWs cannot be overstated; reservoir simulations and management decisions are only as good as the quality of data available. Some of the advantages of drilling ERWs, such as increased reservoir contact, reduced footprint, and fewer wells drilled, will be lost if sufficient reservoir surveillance cannot be achieved. To maximize the benefits of ERWs, creative solutions and innovative designs must be developed continually to push the boundaries further.
Well intervention in horizontal extended reach wells (ERWs) comes with a myriad of challenges and in the case of coiled tubing the overarching impediment is in reaching the target depth (TD). Frictional forces act against the coiled tubing (CT) while being pushed from surface, this eventually leads to helical buckling of the tubing and early lockup where no further progress is made. Advances have been made over the last decade with the development of high-tech downhole CT tractors that deliver a strong pulling force to overcome these frictional forces. Restrictions in the well completion require these tractors to collapse to 2-1/8″, and then to expand to the cased or open hole size of up to 6-1/8″. With many wells having a larger bore size of 8-1/2″, a CT tractor did not exist to improve the coverage in those type of wells. At first glance, modifying the existing tractor for 6-1/8″ sized holes to function in 8-1/2″ sized holes could be accomplished by simply extending the lengths of the arms. However, the reality is a little more nuanced with several innovations required to deliver the same pulling force as the 6-1/8″ tractor version. This new generation of downhole compact high expansion tractors have improved push-links and newly designed grippers to enable rig-less acid stimulation and production logging in ERWs. The high expansion tractor is an important facilitator in CT well interventions to tackle challenging ERWs by increasing the coverage in 8-1/2″ hole sizes. The CT tractor design, development, testing and first deployment was conducted in 2021. The major advantages gained from increasing the reach can be summarized as follows: The CT high expansion tractor enables successful reservoir surveillance and production monitoring, including improved reservoir understanding providing data to update and calibrate reservoir models.Acid stimulation in 8-1/2″ open hole wells on CT targeted fluid placement to improve well productivity to increase revenue per well.Detecting and then shutting off water inflow zones with CT techniques, avoiding the need for drilling a side track. This new generation of slim tractors is the first in the industry to operate in wells with a diameter of 8-1/2″ and an operating range from 8″ to 10″. The key metric to successful acid stimulation or logging applications in ERWs is the ability to achieve maximum coverage of the openhole section. These engineered solutions demonstrate how creative innovations in technology design are improving accessibility in ERWs, resulting in superior reservoir management outcomes.
Electric Submersible Pumps (ESP) are common artificial lift equipment for boosting well productions. One of the challenges faced with ESP applications is the ESP system reliability. High percentage of ESP failures resulted from problems of packer penetrators that locate beneath the ESP packers. These failures could be attributed to the corrosion of the power delivery systems by highly corrosive chemicals and harsh downhole conditions. A method is developed to generate a low density gel system that isolates the electric connector from downhole chemicals in order to provide prolonged protections of electric connectors against corrosive environments. Mixture of low-density polymeric materials can be pumped through the bypass tubing. The mixture has lower density than downhole fluids so that it travels upwards in the wellbore. Under high temperature in the well, a rigid gel system forms and isolates the electric connector from the hostile chemicals thus providing a better protection. The rigid low density gel system was tested in the lab scale. The tested fluid system comprises of colloidal particles and thermal plastic microspheres. The colloidal particles forms a rigid gel under elevated temperature while the thermal plastic microspheres act as light weight fillers. Gelation tests are conducted under different temperature and pressure conditions. The system has a lower density than crude oil and the gelation process can be controlled by chemical concentration. Sealing effects with the presence of crude oil are tested in rusty metal pipe to imitate casing material. A wellbore injection physical simulator was also setup to observe the flow dynamics and chemical reaction that could take place in the wellbore. The field trial test was performed after a through engineering design. Coiled tubing (CT) was selected as the optimum solution for intervention and placing the fluid system. Mixture of low-density materials and gelling agent were prepared on the surface and then pumped into the targeted section utilizing 2.0" coiled-tubing (CT) nozzles. Conventional bottomhole assembly was utilized to seal the tubing section and divert the fluid system to annulus.
Successful stimulation fluid placement in extended reach wells (ERW's) through coiled tubing (CT) is primarily dependent on the depth reached for maximum reservoir contact. Well configurations of minimum bypass (2.4 in.) and openhole sections (6 1/8 in.) are the main challenges for CT reach in these ERW's. Implementation of a CT slim tractor along with fiber-optic enabled cable were applied to overcome the challenges and set a new record for CT reach. CT lockup is the phenomenon that occurs due to friction forces and helical buckling, which limits the CT reach. To tackle these challenges, an accurate simulated lockup depth is estimated using historical data to identify the required pull force. The CT slim tractor (2 1/8-in.) was chosen as the optimum tool to provide the required pull force, as well as pass through the minimum ID restriction of the well. Specially designed tapered CT with fiber-optic enabled cable acquired real-time data from the downhole tension-compression (TC) sub to confirm both the activation and lockup depth of the tractor. The expansion ratio of the tractor from 2 1/8-in. to 6 1/8-in. OH section opens a new era for CT reach in restricted ERW's. The world slimmest tractor passed the 2.44-in. minimum ID restriction and provided more than a 3,000 lbf pulling force, allowing the CT to cover the entire openhole section. Along the way, two new records were recorded for the longest section tractored by a slim CT tractor and the furthest distance travelled in a producer well reaching a TD of 24,706 ft. Increased reservoir contact during stimulation through engineered solutions has set a new standard enabling the implementation of a full stimulation campaign. These engineered solutions demonstrate the potential for CT interventions in extended-reach horizontal wells with completion restrictions, where the main challenge is to maximize the reach for optimum stimulation. As a direct result of several innovative solutions applied simultaneously, a new record for CT reach was set, surpassing the previous record by nearly 5,000 ft.
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