When a well has been diagnosed with formation damage, the norm is for operators to propose reservoir stimulation via acid/solvent pumping. In Field T, located offshore Bintulu in Malaysia, mineralogy understanding is limited as cores available only represent a few reservoirs. For those reservoirs which do not possess representative cores, it is a risk to prescribe any chemical. Historically, acid and solvent stimulation do not hold a good track record in T field. Hence, it is essential seek other stimulation methods that do not involve the requirement for mineralogy.
The UST (ultrasonic stimulation) technology operates on the concept of ultrasonic waves combined with low frequency waves breaking nearby damage up to 1000m into the reservoir. The resonator is conveyed by E-line, hence, possessing a smaller footprint as compared to mobilization of a pumping unit and chemical tanks. Platforms in Field T are small, hence, bringing a pumping package onboard will require hiring a barge due to limited deck space. Seemingly, operational risks are reduced as there is no need for manual chemical handling. The selling point of this technology is minimal well downtime as the stimulation can be performed on a live well, which further reduces possibility of damaging formation during stimulation due to secondary chemical reactions.
UST was piloted on 2 wells in Field T: Well X and Y. Well X showed an initial 30% gain post stimulation. Well Y was showing signs of clogged gas lift valves. Post operation observed pressure communication between tubing and casing which suggests that UST successfully broke the wax that was clogging the gas lift valves. A takeback from this project would be to not only stimulate the target reservoir, but to also stimulate the tubing walls and gas lift valves if there are any suspected valve plugging in the well. This paper will describe the technology that was used to stimulate the well in an environmentally friendly, non-invasive method. For fields with limited mineralogy data and deck space, it is recommended to explore an alternative stimulation method, such as UST, on the wells.