This is the first of two papers which describe a comprehensive multidisciplinary effort toward reservoir characterization in the Greater Burgan field. In early 1995 a team of geologists and engineers began reviewing and evaluating Greater Burgan data in order to build an integrated reservoir model. This paper describes the interpreted depositional history of the Burgan formation, relates water encroachment in the reservoir to the stratigraphic architecture, and discuss the potential for oil migration between the main reservoir units. P. 509

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Greater Burgan Field accounts for most of the oil produced in Kuwait. Discovered in 1938, commercial production from this giant field commenced in 1946 accelerating rapidly to a peak of nearly 3 MMBOPD in 1972. The Burgan structure is an anticlinal dome with numerous faults. The main producing reservoirs are sandstones of Cretaceous age. Four major sandstone horizons within the gross productive section account for most of the current and cumulative production. The 3SM is the main contributory sand which is much thicker than the others. A strong natural water drive maintains reservoir pressure.The compartmentalization of the main reservoir sands by faults, combined with high production rates, resulted in water incursion problems since the early seventies and made worse by uncontrolled flow from wells sabotaged during the Iraqi invasion. As the 3SM reservoir gets further depleted, water encroachment studies reveal that there is a differential rate of rise in OWC in the massive sand implying un-even sweep. This has created uncertainties in the remaining oil column in flank areas of the field for placement of infill well locations. This paper presents a methodology applied to successfully identify infill well locations in flank areas of Burgan field. The behavior of faults and rise in water in different compartments were analyzed utilizing seismic surveys, pressure buildup tests and PNC log data combining with production history. Based on the analysis minor faults were characterized and mapped which led to identification of unswept areas where new well locations were proposed. Gross pay found in three new infill wells drilled have been very encouraging.The process leading to identification of these successful well locations is discussed in length. More infill locations and well intervention opportunities are being identified by using this methodology with increased surveillance to further enhance production from this field.

The Greater Burgan field in Kuwait is the largest clastic oil reservoir in the world. Reservoir simulation in this gigantic reservoir presents formidable challenges in any modeling effort. Its sheer size, complex geology, intricate surface facility network, 2,200 completions, and 58-years of production history with significant uncertainty represented a daunting task in history-match and prediction. The quest began in 2002 with the creation of a 65-million cells' geostatistical earth model. The full-field simulation model of 1.6-million cells consists of six major oil reservoirs (Wara, Mauddud, 3SU, 3SM, 3SL, and 4S) with 145 faults. These faults are major conduits allowing fluid migration between reservoirs. This paper describes the history-matching process used in detail along with the value that has been added through prediction cases run with this model to date. A tiered history-matching approach was used based on field, gathering center (GC), GC-sand and key well-level observations. Also, a full-field net oil column thickness map was used for detailed saturation matching over the entire field. Fault parameters, kv/kh, and aquifer connections turned out to be important history-matching parameters in this exercise. Prediction cases with this model were set up by automatically managing GC-level oil and water handling limits, field-level oil rate targets, facility upgrades, infill drilling schedule, treatment of selective and additional potential wells, and operational criteria for individual well shut-down. Automatic logic to manage all of these features caused a parallel CHEARS (an internal Chevron reservoir simulator) 50-year prediction case run-time to be around 2 days on the 16-CPU IBM Regatta machine using AIX5.1 operating system. Today, it is regarded as the key corporate planning tool for strategic field development and secondary recovery assessment for the Greater Burgan field. This model has been used for Base case forecasting as well as artificial lift, additional 3SU infill drilling, and Wara pressure maintenance project (PMP) evaluations to date. Procedures used to set up these value-added cases will be discussed. The systematic process used in this project for history-matching and prediction will be useful for all reservoir simulation exercises on large fields with a very long history. Introduction Burgan Field, the world's largest sandstone oil field, lies 35 km south of Kuwait City near Ahmadi, Kuwait and covers a surface area of about 450 square miles. The four main reservoir units comprising the Greater Burgan Field complex are the Wara, Mauddud, Burgan Third Sand and Burgan Fourth Sand (4S). Burgan Third Sand is further divided into Third Sand Upper (3SU), Third Sand Middle (3SM), and Third Sand Lower (3SL) units. Some papers(1–5) have appeared in the past discussing reservoir characterization, petrophysical study of residual oil saturation, production data integrity, long-term production forecasting, and flow simulation for the Greater Burgan field. This paper is an attempt to describe the most current and sophisticated flow simulation model of the Greater Burgan field prepared to date within the Kuwait Oil Company. This paper highlights the complexity of this exercise and the results obtained from this model to make strategic decisions regarding field development and facility upgrades.