The original lower completion strategy for the 13 oil producer wells in X Field was open hole standalone screens (OHSAS). The lower completion string comprised 6⅝-in. premium mesh screens inside the 8½-in. open hole. On the basis of updated predrill well data, stakeholders decided to change the well design to a cased hole gravel pack (CHGP). This paper discusses the feasibility study that was conducted to switch the design, the justification used to maintain the original strategy but with an increased use of swell packers for better compartmentalization in the OHSAS design, and the production results of the completed wells.
Based on the most-recent data, maintaining the original design would increase the risk of water breakthrough and subsequently lead to a loss of production. Furthermore, all past campaigns in X Field were completions with CHGPs. To address these concerns, additional studies were performed to evaluate the potential of using the existing inventory combined with the concept of mounting shunt tubes onto the 6⅝-in. mesh screens for CHGP and to evaluate increasing the quantity of swell packers using different swelling materials for OHSAS completions. The assumption was that with a sufficient number of swell packers placed in the open hole with the sand screens, which would create a higher differential pressure, zonal isolation could be achieved in an open hole similar to the effect of having a bypass barrier in a cemented cased hole completion.
Studies have showed that installing shunt tubes for 6⅝-in. screens for CHGP poses additional risks because of the tight clearance inside 9⅝-in. casing, and they can only be mounted with two shunt tubes. Isolation between zones is achieved by means of multizone shunted cup packers. However, as a result of the long lead procurement time for the multizone shunted cup packers, this option requires expediting to meet the project timeline. However, simulations performed on the enhanced OHSAS design using an increased number of swell packers became a promising solution to overcome the water breakthrough problem. The challenges were to determine the optimal quantity of swell packers required and the precise placement along the open hole. Other challenges are increasing drag effect on high dogleg well to accommodate the large quantity of swell packers. Sensitivity analysis of swell packer quantity had been run and compare with existing successful track record to further optimize the completion design.
To meet the budget and schedule for the campaign, OHSASs with swell packers were successfully installed in Q4 2021 to isolate the water contact zone in the first three wells. Additional swell packers and short screens were used to mitigate the water-production risk and enable the completion and isolation of thin zones. Well unloading was performed immediately following the completions, with positive results in terms of water production in two of the three wells. The production performance of these three wells will be evaluated to determine the sand-control design strategy for the remaining wells on the next platform in Q3 2023.
