The new generation of Power Water Injectors (PWI) wells with longer open-hole (OH) horizontal section has been grown significantly in Saudi Arabia especially in the new development fields. One of these new complex fields have been developed with over 120 PWI wells with OH sections in the range of 2,000-10,000 feet. While the long OH horizontal wells have several advantages, they also have a challenge for the rig-less intervention. This paper summarizes the development and enhancement of techniques implemented during the acid stimulation treatment of extended-reach wells using CT without mechanical assistant tools like vibration or CT tractors. During the initial CT interventions in this field, several challenges were encountered, e.g., stuck CT due to pressure differentials and slack-off weight due to sudden dogleg or azimuth changes. Previous simulations and studies resulted to a combination of techniques to the CT intervention procedure to extend the CT reach and minimize the operational problems and costs. Remarkable improvements were achieved by performing additional simulation runs, correlating the CT weight loss vs. the horizontal sections geometry and analyzing all available operational data. By incorporating enhanced intervention procedures based on the lessons learned from the previous jobs, a new reach records were achieved successfully on the wells with over 7,000 ft. As a result, additional cost savings were realized since most of the extended reach wells were stimulated without using CT tractor. One of these wells reached a total measured depth of 5 km and horizontal OH length of 3 km, which is the longest record in the region.

The foremost purpose of carbonate matrix acid stimulation is to improve near wellbore flow conductivity, induce the desired conduits, and bypass the formation damage. Hydrochloric acid (HCl) is the most predominantly used treatment fluid to treat carbonate formations, enhance permeability, and amplify contact with the formation. Unlike sandstone acid stimulation, which experiences a relatively uniform acid front, carbonate formations experience a very high surface reaction rate, and so affecting the overall surface area in contact with the acid, which eventually leads to nonuniform distribution of stimulation fluid. The condition gets even more intricate in tight carbonate formations where the formation characteristics are prone to higher heterogeneity. Prominently, the fluid flow will follow the path of the least resistance regions, leaving behind the lower permeability strips unswept. Therefore, to combat the aforementioned issues with the distribution of stimulation fluid, a patented state of art multi-jetting tool technology was invented and introduced to ultimately boost the acid stimulation efficiency. The multi-jetting tool is deemed to offer deeper, more efficient penetration of injected fluids using a combination of pulsating action and helical flow from jet ports of more than 6" penetration radius with relatively low-risk in cleanout and stimulation operations. This is contrary to other jetting tools that constitute laminar flow patterns which cease its effectiviness 3" penetration radius. It is a very robust jetting tool with minimal failure rates since it has no internal moving parts or seals, which in turn offers high degree of reliability. This tool was proposed to promote production or injection from noncontributing intervals by selective stimulation treatment while manipulating the pumping rate and pressure to avoid surpassing the fracture gradient of the well. The multi-jetting tool conveyed on coiled tubing was employed to acid stimulate tight reservoir formation salt water disposal well. It has exhibited numerous advantages. The tool has leveraged its oscillation/agitation features to reach the TD effortlessly without the need to induce friction reducer during the operation. In addition, a reduction in pumping time by 33% was attained since the tool has managed to pump at a noticeably high average rate of 3.2 bpm with a clear reduction pumping pressure from 4,200 to 3,800 psi signifying that the formation has responded to acid treatment. This paper provides a brief technology overview of this multi-jetting tool and tool operation, and benchmarks its efficiency against the conventional jetting techniques with an emphasis on the distinctive characteristics compared to the existing tool in the industry. The paper presents the tool deployment and acid stimulation trial test execution and results, recapitulates conclusions about the tool performance, and identifies a number of recommendations.

This paper presents a comprehensive injection performance analysis conducted in major carbonate fields in Saudi Arabia. The production from the fields under study is pressure-maintained by peripheral water injection. More than 190 case studies were examined to generate populated trends and draw relevant conclusions on parameters affecting injection performances. Petroleum engineering concepts/tools, such as pressure transient analysis, were heavily used in this work to establish the effective yearly injection decline rate for each well.Extensive and dedicated sampling of injected water was carried out as part of water quality monitoring to ensure that well plugging and internal corrosion was minimized. The total dissolved solids, total suspended solids, particle count and size distribution, acidity, iron count, sulfide content, and bacterial growth data were measured and synchronized with the respective wells' injectivity indices to identify potential sources of well injection impairments. Major events, such as when starting or switching the water injection system, were thoroughly factored into the water quality analysis and its subsequent effect on the injection performances.The well injection performance analysis was carried out using pressure-transient analysis data obtained from Fall-Off Test (FOT) surveys, where each well has a baseline II survey taken when the well was first drilled and completed. Dimensionless injectivity indices were defined to compute the injection potential of each well. Baseline surveys were then compared with the subsequent or the latest surveys, if any, based on which time-lapse measurement trends were generated and analyzed.Several key findings and recommendations, regarding setting appropriate limits to water quality parameters and injection surveillance strategy, are presented in light of the performed analysis.This paper also discusses production engineering efforts to mitigate the decline in well injectivity, including: water quality control, well stimulation initiatives to enhance injectivity, and analysis of well plugging characteristics/profiles and their relation to reservoir permeability.