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Industry Article: Redefining the Stimulation Strategy

A real-time downhole flow measurement service on coiled tubing boosts success in open-hole water injectors, in Kuwait

Publication: World Oil
Publication Date: 10/01/2017

by Mohammad Rashed Al-Othman, Nasr Bader Al-Houti, Mariam Al-Shuaib, and Hamad Saeed Al-Mehanna, Kuwait Oil Company and Wael Mahmoud and Pierre Ramondenc, Schlumberger

Matrix stimulation to improve injectivity by pumping acid into the rock to bypass deposits that inhibit flow and open new pathways to the reservoir has historically been performed indiscriminately from the surface. This blind acidizing method results in uneven distribution of the fluid, with some zones being over-stimulated and others not receiving any treatment. Operators must then deploy production logging tools in multiple runs downhole to identify favored pathways and determine which zones are not being stimulated, adding considerable time, cost and logistics to the operation.

A new stimulation strategy

Confronted with multiple challenges in a secondary recovery program using seawater injection, Kuwait Oil Company implemented a new downhole flow measurement system capable of reducing runs into the wellbore, while improving fluid placement and management to achieve a faster, more informed matrix stimulation in two wells.

A pre-stimulation profile for one well showed that most of the seawater was being injected at the heel and toe of the well, with nearly 60% of the open-hole section receiving very little or no water at all. Even after multiple acidizing treatments, both wells experienced productivity declines over time. Using the Schlumberger ACTive Q CT real-time flow measurement service, KOC was able to target the thief zones with a chemical diverter and stimulate the tight section of the open-hole section with acid.

Real-time flow measurement

Engineered to simultaneously profile horizontal sections and treat them in a single run with same bottomhole assembly, the service enables operators to evaluate the flow rate contribution to each interval and assess zonal coverage during treatment to accurately place the fluid and control where it goes in real time. Data is acquired by the ACTive DFLO CT real-time flow measurement tool, which provides real-time readings of multiple downhole parameters, all conveyed to the surface through fiber optics on CT.

The stimulation strategy for the two KOC wells involved isolating both the toe and the heel of the wellbore and targeting the middle section with a high-strength acid placed between the two extremities of the horizontal section. CT was run in the hole to the end of the production tubing, where depth correlation was performed, and then run in the horizontal open-hole section. Flow velocity profiles enabled KOC to adjust volumes of both the acid and diverter pumped along the open-hole sections.

More uniform injection profile

Both injectivity and flow distribution showed a marked improvement. Rebalancing the distribution of the injection in the reservoir resulted in a more sustained injectivity increase and delayed the water breakthrough in nearby oil producers, eliminating the need for costly remediation. By opening the wells’ middle sections, KOC achieved a more even downhole flow distribution along the horizontal open-hole interval, with the middle sections accounting for nearly 40% of the flow after treatment.



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