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The Greater Burgan Field consists of three sub fields (Ahmadi, Burgan and Magwa). Drilling commenced in this field in 1938 and it went on stream in 1946. Most of the production comes from a giant oil reservoir in a siliciclastics depositional environment. This giant oil reservoir has intercalating sand shale sequence with the upper part having mixed lithology. Co-existing together are argillaceous glauconitic sandstones, calcite, dolomite and anhydrite with pyrite and siderite. With increasing demand of oil in the world, it has become necessary to improve oil production. As a result, the various field development assets of Kuwait Oil Company (KOC) are tasked to increase the number of horizontal wells in order to access thin reservoirs in the field. This has prompted these teams to increasingly rely on Logging While Drilling (LWD) services as well as improved geosteering practices in order to efficiently access the untapped energy resources buried several thousand feet below the earth's surface. Evaluating these wells becomes an issue especially if the wells are drilled in areas that might add to the reserves of the asset. Resistivity anisotropy is a major issue, especially if it occurs with influence of other bed boundary effects like resistivity of adjacent beds or polarization horn effects. Water coning issues in the field makes it even worse to interpret the resistivity data as they become spiky. Complexity of the resistivity signature in a mixed lithology environment makes petrophysical evaluation difficult. With the recent introduction of the Multi-Function LWD tool where most of the basic measurements are collocated in one LWD collar, it is now possible to make measurements with similar environmental influence prior to significant invasion of the formation. In addition, the introduction of capture gamma ray spectroscopy and formation sigma in real time has improved the petrophysical evaluation of this complex resistivity environment with mixed lithology in wells that are difficult or even costly to consider wireline logging. This paper aims at highlighting horizontal well drilling issues occasionally encountered in the Greater Burgan Field and the recent introduction of the Multi-Function LWD service to help address these formation evaluation issues.

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Since, the discovery of the Mid-Cretaceous Mauddud formation in the Sabriyah and Rhaudhatain fields of North Kuwait, there has been an interest to systematically produce the thick (> 400 ft) carbonate-dominated section, which has a complex geological setting that influences the performance of these reservoirs. Several wells have been drilled in the past-deviated, vertical, and horizontal wells focusing solely on the carbonate-dominated reservoir section with little emphasis on the siliciclastic shoreface facies of the lower Mauddud formation.The use of state-of-the-art real-time logging-while-drilling (LWD) data from the distance-to-boundary (DTB) resistivity mapping technique coupled with normal triple combo LWD formation evaluation log measurement and real-time pressure and mobility estimations provides insight into the lateral facies changes and the heterogeneity of the MaH reservoir layer for the first time.The predominantly carbonate Mauddud formation stratigraphically overlies the greater Burgan member. It was deposited in a low-to high-energy shallow marine ramp setting. The high-energy facies at the base is punctuated with out-of-sequence siliciclastic influence marking the waning of the deltaic Burgan sand influx. The upper part of the Mauddud formation is a highly diverse suite of low-energy carbonate facies characterized by highly bioturbated and reworked massive beds of wackestone and packstone with few depositional textures. This section is overlain by the prograding clastic sediments of the Wara formation and capped by the extensive transgressive shale of the Ahmadi formation.Well A (SA-0X05), the appraisal well, was planned to cut across all the Mauddud 10 reservoir layers and go lateral into the MaH reservoir with 100% NTG, thus yielding maximum reservoir contact (MRC) to evaluate this sand body for the first time. The results from porosity measurement validated the static model for this interval, and the pressure regime and mobility where inline with predicted values considering vertical variations. Lateral facies changes were observed showing coarsening-upward, clean-grained facies towards the base and the fine-grained glauconitic facies on top. Although an approximate20-ft thickness of sand was observed as a correlatable sequence from offset wells, in reality, geosteering revealed that the lower 15 ft of section was mostly distal in origin and changed to a more marine offshore facies below.

TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractThe Wara Sandstone reservoir in the Minagish Field of Kuwait Oil Company is a complex deposition of a typical pro-deltaic environment. The sedimentation starts from tidal marine deposition containing beach sands and lagoonal facies that are subsequently overlain by fluvial channel sands. The bases of the channel sandstones have in many cases an erosional contact that cuts into the underlying sequence. The marine sandstones are of much finer grains and poorer quality than the overlying channel sands that are generally coarser in grain size, thereby having better porosity and permeability. On top of the channel sequence, a marsh overbank or lagoonal environment overlay and are characterized by silts and coaly layer sequence. They are also finalized by a subsequent deposition of progradational coastal marine silts and fine sands. All these deposits find their high stand in the overlying Ahmadi formation.The sediment sequence is repeated up to four times and zero to four channels may develop and intercepted by drilled wells depending on the well location within the field.Within this channel sand bodies are different lobes that contain varying degree of minerals from glauconite to anatase, pyrite and hematite with other cement materials like calcite. The matrix materials in the more shaly intervals are predominantly illite and glauconite. Glauconite occurrence was either deposited via transportation (detrital) or generated during early diagenesis to act as cement materials. Glauconite cement has a strong impact on reservoir producibility and since it is present throughout the entire sequence of depositional events, it plays a great role in the petrophysical evaluation of the reservoir.Being able to geosteer within the sand bodies will require proper understanding of the depositional environment and thus requires discriminating intervals with relative abundance in glauconitic grains as they impact reservoir quality.It has been proven from previous core studies that the more the detrital glauconite occurrence, the greater is the relative abundance of glauconite cement as well. In this paper we propose the use of increase in the presence of iron (Fe) dry weights with its associated Titanium from the multi-function logging while drilling (LWD) tool to discriminate the relative abundance of glauconite in the reservoir sand bodies, thereby characterizing the lobes. We will also highlight the benefits derived from using the formation sigma in real time for petrophysical interpretation and its usefulness in deciding intervals to perforate in horizontal well drilling.