Tariq K. Siddiqui, Hassan M. Al Khatib, and A. Junaid Sultan, Zakum Development Company (ZADCO)
SPE Members
Abstract
Drilling deviated wells in the Upper Zakum field did not allow to develop this field to its full potential. It is an offshore field, only a limited number of platforms are available. Therefore, it may become uneconomical to drill a large number of deviated wells for the full development of the reservoirs. Application of horizontal wells in this field helped in redeveloping the reservoirs.
Data were integrated from different petroleum engineering disciplines and analyzed to identify problems in the reservoirs. Horizontal wells played a vital role to resolve various problems faced in different parts of these heterogeneous reservoirs.
This paper reviews the field development strategy which was further refined with time as more horizontal wells were drilled in this field. Performance of horizontal wells have been compared and evaluated with the deviated wells. A brief discussion on drilling, completion, and stimulation procedures used for horizontal wells has also been included.
This study contributed to some extent in resolving reservoir problems ranging from enhancement of productivity index, development of reservoir flanks, and recovering un-swept oil from water flooded layers with the applications of horizontal wells
Introduction
FIELD
The Upper Zakum field is located offshore, about 80 Km North-West of the city of Abu Dhabi in the Arabian Gulf. The full field development was started in 1977. Production commenced in 1982, and pattern water injection started in 1984.
GEOLOGY
The Field produces from the lower Cretaceous limestone, which is an anticline trap. The reservoirs petrophysical characteristics are generally better in the crest and gradual deterioration of rock properties (porosity, permeability) take place towards the flanks.
The field is comprised of three major zones (Thamama I, II, and III) overlying each other. These zones are further subdivided into six main producing reservoirs (I, II, IIIA, IIIB1, IIIC, and IIID-H), which can be seen in Figure 1.
Reservoirs I and II (or Thamama I, Thamama II), which are the main subject of the discussion of this paper, are further subdivided into sub-units. Reservoir I is divided into six sub-units (L1/L2, L3, L4, L5, L6, and L7). Reservoir II is divided into thirteen sub-units, seven subunits(11A0, HA, lIB, IIC, IID, IIE, IIF) correspond to porous layers and six intervening layers are the dense zones. The development of these reservoirs has been discussed in the following section.
P. 397
