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The Who Dat field is located in Mississippi Canyon 503 under 3,100 ft of water, penetrating 11 stacked horizons between 10,000 – 18,000 ft, in Pliocene and Upper Miocene age. The Who Dat OPTI-EX® semi-submersible FPS was the first FPS built on speculation, and was the first privately owned FPS in the world. The field was discovered in December 2007, initial production in December 2011, and the field paid out in 2014. The field has produced more than 52 MMSTB of oil and 99 BCF of gas as of year-end 2017. This paper will cover the integrated reservoir study of the Who Dat field, which includes geological modeling, data management, reservoir surveillance, construction of the integrated reservoir models, history match and forecast of the integrated models, depletion plan optimization, production operation optimization, sensitivity, and uncertainty analysis. The eleven different horizons in the Who Dat field have various depositional environments, petrophysical properties, and fluid properties. As a result, the optimum depletion plan needs to be uniquely designed for each reservoir, as well as for the field as a whole. The biggest reservoir, the 4600, exhibited steep pressure decline and great connectivity which made it a potential candidate for water flooding. However, the facilities do not have space or weight capacity for the water flood equipment, which leaves only high cost solutions such as major platform modifications (wing decks, hull blisters) or building a standalone facility on the Shelf. Based on a thermal simulation model, the injected cold water viscosity is several times higher than the in-situ water which decreases the injectivity of the water injectors. Even though the water flood project was expected to increase ultimate oil recovery significantly, the project team recommended not going forward with the project based on the integrated reservoir study and the resulting economics. If the water flood project was sanctioned, the field would not pay out for years and the net present value of the project would be significantly decreased. The second biggest reservoir, the 4700, had a downhole sample showing undersaturated oil with a GOR of 1,280 SCF/STB; however, the well experienced an abnormally high 4,500 GOR when put on production. A later well that penetrated the updip area showed the zone to be gas bearing, which indicated the reservoir is not in equilibrium with a gas cap and undersaturated oil rim. The project team decided to decrease the rate to see whether the well was rate sensitive. With the help of multiphase meters, the team observed that with decreased rate, the GOR dropped to less than 2,500, and the productivity index increased from 4 stb/psi to 14 stb/psi. By continuing to produce the well at a reduced rate the ultimate recovery significantly increased. The reservoir models have been very consistent after a couple of years’ production. The production and pressure forecast from the 2014 history matched models are within 10% of the historical data, which provides confidence in the integrated model. After 6 years of production, the project team is still actively updating and utilizing the integrated models to evaluate future development wells, secondary recovery opportunities, and production optimization to further increase the value of the Who Dat field.
This paper provides an overview of the Who Dat development. The Who Dat fieldis located in the Mississippi Canyon protraction area of the Gulf of Mexico inblocks 503, 504 and 547 and is being developed using the OPTI-EXsemisubmersible floating production system (FPS) which has a capacity of 60MBOPD and 150 MMCFD. The Who Dat discovery is primarily oil and consists of tenstacked amplitude-supported reservoirs in a salt withdrawal mini-basin. Threewells have been drilled to date penetrating over 700' of net pay in ninedistinct reservoirs ranging in depth from 12,000' to 17,000' TVD. The fieldwill be developed with twelve subsea wells (i.e. wet trees) flowing to threesubsea manifolds and subsequently to the FPS via two infield flowloops usingflexible risers. The project includes a 10" gas export line and 14" oil exportline also using flexible risers. The paper covers the exploration phase including evaluating the prospect priorto the lease sale and adjusting the delineation plan based on the discoverywell. The paper also covers the development concept selection including theevolution of the project from a long subsea tieback to a new FPS, thechallenges of utilizing an FPS that was built on a speculative basis(modifications required, regulatory approval), and contracting strategy(negotiation of an installment purchase and managing uncertainty in apost-Macondo environment). This development represents a number of firsts: first time that a privatecompany will own an FPS, first time the OPTI-EX semisubmersible FPS will beused, first time an FPS has been approved for installation post-Macondo, firsttime an FPS has been built on speculation, and first time a field has gone fromconcept selection to installation of a new FPS in less than a year. Theproject's accelerated schedule created challenges since numerous items were oncritical path, including items that are typically nowhere near criticalpath. New Seismic Shows Previous Wells were Drilled in Poor Locations. There were a number of amplitudes (bright spots on the seismic data) that werepreviously identified in the Who Dat Area. The objective section, LowerPliocene though Upper Miocene had been drilled in offset blocks MC 460/502/546. The wells were drilled in these blocks from 1985–1998 and found thin and/orpoor quality hydrocarbon bearing sands. Operators presumably assumed that theresults of these wells meant that all of the amplitudes in the area were thinand uneconomic which is the likely reason British Borneo allowed blockMississippi Canyon Block 503 (MC 503) to expire without drilling a well. Withthe release of the TGS MC Revival PSTM 3 D data set in the spring of 2004 overthis area, the poor placement of these wells and the thin pay results werebetter explained. This did not alleviate the risk of finding thin pays in otherwells but LLOG felt it could explain the poor result.
This paper provides an overview of the Delta House Project. The Delta House Floating Production System (FPS) in located in the Mississippi Canyon protraction area of the Gulf of Mexico in block 254 and will initially process production from three "anchor" fields varying from six to fourteen miles from the FPS. The FPS uses the Exmar Offshore designed OPTI-1100® semisubmersible design which has a nameplate capacity of 80 MBOPD and 200 MMCFD with peaking capacity of 100 MBOPD and 240 MMCFD. The Delta House anchor fields are primarily oil bearing Miocene sands in a channel levee turbidite depositional environment. Seven wells have been drilled to date in the initial anchor fields. Each anchor field will be developed with (i.e. wet trees) flowing to subsea manifolds and subsequently to the FPS via two infield flowloops using steel catenary risers. The project includes a 12" oil export line and 16" gas export line using steel catenary risers. There are several unusual aspects of the Delta House project. The project went from first discovery to first production in about three years which is significantly less than other projects involving a new FPS. Engineering for the FPS and bidding of construction yards began prior to the first Delta House discovery. The Delta House FPS and export lines are owned by special purpose entities funded primarily by private equity. This paper will provide a history of the project and will highlight the reasons for some of the key decisions that were made throughout the development.
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