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.

Rigless well commissioning is an important stage of well completion to deliver a new drilled or worked-over wells (oil producer or water/gas injector) ready for production or injection. Rigless well commissioning employs firstly slick wireline intervention for well accessibility verification, down hole safety valve operability, bottom hole pressure and fluid gradient survey that assists to design the flow to clean commissioning program. Secondly, it employs coiled tubing (CT) and flow to clean (FTC) packages to cleanup the well and if necessary to perform matrix acidizing to improve well productivity or injectivity. This paper highlights operational constraints of well commissioning and its effective approach from job design, execution and evaluation that have been performed over 250 wells in the span of 5 years operations. The commissioned wells are drilled in the carbonate formation with surface clustered operation in Onshore and Offshore Artificial Islands. It also describes HSE challenges that have been faced in safe handling of return fluid, management of volatile recovered crude oil, simultaneous operations (SIMOPS) with Drilling Rig, Project and Construction (P&C) activities and hydrocarbon flaring in the environmentally sensitive area. The implemented approach and methodology of well commissioning has evolved significantly to address operational challenges and reducing well commissioning cost by 60%. It proves improvement of operating efficiency of CT and FTC packages based on downhole pressure survey, smart well commissioning, eliminating high risk clean-up operation for injector well, cluster based well commissioning, in-situ return fluid management and arrangement of vertical flare stack in the constraint offshore artificial island. The overall outcomes have achieved technical objective with optimized cost and minimum risk, enhancing rigless package utilization and implementing sustainable and effective field rigless commissioning.

Over the past decade, coiled tubing (CT) has been one of the preferred fluid conveyance techniques in tight carbonate oil producers completed with an uncased horizontal section. In the onshore Middle East, conventional CT stimulation practices have delivered inconsistent results in that work environment. This is mainly due to a mix of reservoir heterogeneity, limited CT reach, lower CT pumping rates, uncontrolled fluid placement, and uncertainty of downhole dynamics during the stimulation operations. An intervention workflow recently validated in onshore Middle East to acidize tight carbonate openhole horizontal water injectors was introduced for the first time in an oil producer. The advanced stimulation methodology relies on CT equipped with fiber optics to visualize original fluid coverage across the openhole interval through distributed temperature sensing (DTS). Real-time downhole telemetry is used to control actuation of CT toolstring components and to understand changing downhole conditions. Based on the prestimulation DTS survey, the open hole is segmented into sections requiring different levels of stimulation, fluid placement techniques, and diversion requirements. The candidate carbonate oil producer featured an average permeability of 1.5 md along 8,003 ft of 6-in. uncased horizontal section. Because of the horizontal drain's extended length and the presence of a minimum restriction of 2.365-in in the 3 1/2-in. production tubing, a newly developed CT slim tractor was essential to overcome reach limitations. In addition, a customized drop-ball high-pressure jetting nozzle was coupled to the extended reach assembly to enable high-energy, pinpoint acidizing in the same run. The instrumented CT was initially run until lockup depth, covering only 53% of the horizontal section. The CT slim tractor was then precisely controlled by leveraging real-time downhole force readings, enabling full reach across the open hole. Prestimulation DTS allowed identification of high- and low-intake zones, which enabled informed adjustments of the acidizing schedule, and in particular the level of jetting required in each section. After its actuation via drop-ball, the high-pressure jetting nozzle was operated using downhole pressure readings to ensure optimum jetting conditions and avoid exceeding the fracturing threshold. Upon completion of the stimulation stage, post-stimulation DTS provided an evaluation of the fluid placement effectiveness. After several weeks of production, the oil rate still exceeded the operator's expectations fivefold. This intervention validates the applicability of the advanced matrix stimulation workflow in tight carbonate oil producers completed across a long openhole horizontal interval. It also confirms the value of real-time downhole telemetry for optimal operation of extended reach toolstrings and the understanding of the downhole dynamics throughout stimulation treatments, the combination of which ultimately delivers breakthrough production improvements compared to conventional stimulation approaches, in a sustainable manner.