Oil Production in Gulf of Thailand Offshore has always been hijacked by high water-cut. Field recovery suffers with most sand RF<10% due to premature water breakthrough and by-passed oil. Connecting sand pockets of varying sand quality and huge heterogeneity contrast for commingled inflow has further worsened non balanced production, especially in the progressive development towards horizontal wells' production. However, the deployment of downhole flow control (ICD) in Field-BY as pilot, has revolutionised conventional surface-choke controlled production towards downhole nozzles' inflow and drawdown control. The ICD's pilot, BY-A is selected based on its strategic comparison-value to an existing horizontal well, i.e. BY-B, completed with sand-screen standalone, SAS in the same sand and about the same horizontal length. An 'apples-toapples' evaluation comparison over the same production time-lapse between ICD-case and the SAS base-case post-job production demonstrated that the ICD's pilot has prevailed in many production factors and completions strategy as such:i.ICD's well BY-A with ~2 months delay of water breakthrough, unlike BY-B of instantaneous water breakthrough with 40% water-cut in the same period.ii. BY-A has produced >50,000 barrels more oil than that of BY-B for the first 7-months iii. ICD's application has freed up conventional surface choking-back control upon breakthrough. Instead, more liquid rates are pumped at controlled water-cut that transformed previous production to more rates with more oils.iv. ICD's design and modeling, updated with LWD-derived data near real-time, has optimised the completions cost. Effectively, lower ICD's screen completions are applied only at sand-contact.In brief, the entire ICD's design and support together with the post-job production monitoring and optimisation will be discussed. This work provides an insight into transforming an otherwise ordinary horizontal well with typical high water-cut constraints into one of the guiding successful ICD's well that has warranted more ICD's application in the operators other nearby field developments. Field Introduction and Production ChallengesField-BY is located in Block 5/27 offshore Gulf of Thailand, on the northern flank of the Pattani Basin as shown in Figure 1. It is operated by Mubadala Petroleum (Thailand). In most reservoirs, the shallower sands are fluvial channels while the deeper layers are lacustrine deposits. The resulting reservoir geometries are complex in lateral extent and vertical heterogeneity intertwined with shoreface, stacked and extended channels and/or individual channeled sand pockets, for example the targeted TX 75083-3836, U.S.A., fax +1-972-952-9435
For a producing field, oil-water contact movement, gas cap expansion/shrinkage and residual oil saturation (thus the sweep efficiency) are key reservoir dynamic properties for resource estimation and proper reservoir management. Jasmine field in the Gulf of Thailand first began oil production in June 2005. Light oil & gas has been produced from multiple high permeability fluvial sandstones of Miocene-Oligocene age. After more than seven years of development and production, reservoir monitoring becomes even more critical in decision making for well recompletion, drilling of new infill wells and overall fluids management. To understand fluid movement, pulsed neutron logging, including inelastic spectrum (carbon-oxygen ratio, C/O), thermal decay time (Sigma) and cased formation resistivity have been widely employed to evaluate formations through casing. However, each technology has its advantage and limitations. There are three major challenges for formation evaluation through casing in Jasmine field: Formation water is relatively fresh so it is very difficult to distinguish oil from fresh water with pulsed neutron capture (PNC) Sigma.In undertaking hydraulic workover operations, sea water has to be used to kill producing wells before logging, and therefore deep invasion is experienced in perforated zones with high permeability (multi Darcy) sandstone reservoirs. This can result in high uncertainty in oil saturations derived from C/O and partially to cased hole resistivity.In the deeper Oligocene reservoir section, massive shaly sands with low resistivity low contrast (LRLC) pay with high water saturation are present. Fluid typing in such strata is problematic even with open hole resistivity data. To address these various challenges, a combination of cased hole resistivity and pulsed neutron inelastic spectrum, thermal decay porosity & Sigma data have been employed used to reduce water saturation uncertainty and achieve multiple reservoir monitoring and formation evaluation objectives. Results from several logging campaigns since 2009 demonstrate the advantages of using these technologies in-parallel. Utilizing case studies, this paper summarizes the technical challenges and reservoir monitoring solutions as applied in the Jasmine field, including: Gas cap dynamics & OWC movementUnproduced perforated zones in commingled completionsUnswept portions of perforated zonesLow resistivity, low contrast shaly sand evaluation through casingReducing uncertainty in saturation estimation on sands killed by sea waterInputs to resource estimation, reservoir simulation and production optimization
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