Abstract
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.
