Given the recent unique economic challenges and continued need to optimize lower completions, a new approach was successfully implemented offshore by Dubai Petroleum Establishment (DPE), an oil operator headquartered in Dubai, United Arab Emirates (UAE). In the unconventional carbonate source rock Shilaif formation at 8,400 ft true vertical depth (TVD), hydraulic fracturing including proppant was coupled with an openhole multistage (OHMS) ball drop sliding sleeve technology –– a first for offshore completions in the Middle East. This paper will discuss previous completion designs including acid stimulations and most recently an un-cemented completion liner using hydraulic fracturing and proppant. Having matrix-acidized the conventional carbonate formation on previous wells, DPE looked toward improving their stimulation methods for tight unconventional source rock to further enhance the recoverable reserves and continue to optimize the completion.
Key factors evaluated before deciding to use the ball-drop activated sliding sleeves over the traditional plug and perforate (PnP) method of completion were benefits to safety, recovery potential, previous positive experience with the completion method, ease of installation, the ability to continuously pump the stimulation without shutting down (a large benefit in offshore completions) and a significant cost saving. A new technology was also implemented to confirm in real-time that the sliding sleeves functioned. Until now, surface pressure responses were the only indication the sleeves had functioned. This new technology allowed for real time sleeve shift verification that was independent from the usual pressure signature.
The application required a unique, fit for purpose, completion system due to the demanding environment created by both the offshore conditions and the 15,000 psi differential rated equipment requirements for high stress unconventional rock. The tools were engineered, manufactured, and installed in a narrow timeframe that met the demanding offshore rig schedule. The system was then stimulated with a maximum surface treating pressure up to 10,000 psi in a continuous pumping operation. A total of 8 stages were successfully hydraulically stimulated with proppant without any major issues. All balls landed and shifted their respective sliding sleeves which were verified by real time pumping pressure response monitored at surface and independently with the new well monitoring technology used on this well, transmitting data to the main office.
The technologies, methods and procedures presented in this paper are intended to show how DPE is leading the way in the region in reducing completion costs while safely working offshore. The completion solutions engineered and implemented for the placement of these offshore multistage proppant fracture stimulations have allowed DPE to unlock a significant volume of hydrocarbon reserves in the Dubai acreage, if not in the whole region.