Enhanced Reservoir Characterization with Horizontal Well Logs in Dukhan Field, Qatar

Abstract

Over the last decade, horizontal drilling has played a significant role in the development of the Dukhan field in Qatar. Optimal placement of high-angle and horizontal wells has ensured economic hydrocarbon production in the Arab oil reservoirs. In the Arab C reservoir interval, stratigraphic layers are generally thin and exhibit a high degree of lateral variation in rock properties and low to medium permeability. Horizontal producers with long lateral sections have increased ultimate recovery by providing greater penetration of oil columns above oil water contacts and by tapping attic oil and isolated reservoir compartments. Sweep efficiency has also been improved through horizontal well waterflood programs. Advances in rotary steerable drilling and logging-while-drilling (LWD) technologies for horizontal wells provide new types of data that can be used for improved reservoir characterization and geologic modeling. LWD sensors are used at Dukhan to acquire real time petrophysical measurements and LWD image logs are now routinely acquired along with conventional triple combo logs (density/neutron/resistivity). A specialized workflow was developed to utilize the LWD image data in log interpretation. This workflow consists of interpretation modules that can be used to define formation bed boundaries and quantify formation property variations along horizontal wellbores. These definitions of 3D bedding structure data and formation properties are then used to condition the geologic model structure and update cell properties. Image logs and petrophysical interpretation results from several horizontal wells will be presented. Comparisons with offset vertical wells are made to illustrate the added value of using horizontal well data in reservoir characterization. Significant uplift in geological modeling is also achieved by incorporating lateral property variation identified through horizontal well petrophysical evaluations. Introduction Dukhan Field, discovered in 1939, is one of the major oil fields in the Middle East region. The first discovery wells were based on field mapping of the Dukhan anticline (Trabelsi et al., 2009, Stephens et al., 2009). The field forms a north to southeast trending anticline that is 70 km long and 8 km wide (Figure 1A). The anticline culminates in four distinct domes, which roughly correspond to the major divisions of the field. These are, from north to south, the Khatiyah, Fahahil, Jaleha, and Diyab sectors (Figure 1B). A series of extensive studies have been done to characterize the environments of deposition and to define a consistent sequence stratigraphic framework (Figure 2). Production of the Arab C and D reservoirs started in 1949 and has progressed through various phases of the oil field development.