ADNOC has started several years ago few CO2 pilot projects to explore its feasibility for Enhanced Oil Recovery (EOR) in Rumaitha oil field in United Arab Emirates. The CO2 injector wells, to be discussed in this paper, were completed with open-hole horizontal completion, aiming to maximize CO2 injectivity by increasing the contact area between a wellbore and the formation. However, logging these wells for surveillance and intervention has been a challenge, due to the corrosive wellbore environment, tubing minimum restriction and depth reach limitation for both Coiled Tubing (CT) and conventional Tractor conveyance.
The current study focusses on using new Slim-hole Tractor, run first time worldwide in CO2 injector wells to convey the logging tools across these long open-hole horizontal wells for rig-less reservoir monitoring and injection optimization.
The advanced design Slim Tractor uses high expansion and reciprocating system for increased contact area with the wellbore, to convey logging tools in the horizontal open-hole and cased-hole completions. Several improvements were made over the existing conventional Tractors, such as the increase of pull out of hole capabilities, increased debris tolerance, improved gripping and be able to operate in sour environments. Furthermore, logging while tractoring feature for this advanced Tractor is a key differentiator in horizontal logging to achieve logging objectives the earliest possible while minimizing the acquisition time, reducing the footprint on the well sites, hence less HSE issues and better operations efficiency.
This paper presents field experiment conducted on 3 wells in Rumaitha field. The Novel Slim Openhole Tractor was run successfully, first time worldwide in CO2 injector, to convey multiphase production logging tool across a long openhole horizontal completions, in order to determine CO2 zonal injectivity, investigate the presence of possible thief zones, CO2 flow behind the casing. These jobs were conducted real-time to optimize the logging operation and reduce CO2 exposure on the tools. Over 30,000 ft successful tractoring across the 3 horizontal openhole wells. Tractor depth reach exceeded the expectations, almost 100% achieved in 2 wells. The Slim Tractor has also successfully negotiated and passed across multiple washout zones and restrictions encountered, without any issues and the tools were retrieved to surface without any debris clogged on the Tractor arms.
Excellent data quality was acquired from the multiphase production logging tool and pulsed Neutron tool during shut-in and flowing at different injection rates in extremely shorter time compared to CT, saving days of operating time.
This study helped to delineate the conveyance strategies to be adopted in the upcoming CO2 openhole wells and contributed to enhance the understanding of zonal injectivity distributions across the reservoir. The results will be also incorporated into the reservoir model to understand the effect of injectivity on pore pressure, fracture and faults initiations and their effects on sweep efficiency in EOR and Carbon sequestration in carbon storage projects.
