Throughout the UAE and the wider region, several broadly E-W orientated structural lineaments are observed on seismic within the Cretaceous successions and are described as strike-slip faults. However, in the studied field, these features have not been readily observed in well data. Instead, networks of fractures and deformation features are present in core and borehole images. A study was carried out in an attempt to calibrate well and seismic data and to understand the relationship between the seismically-resolved faults and the fractures observed on core. This study focuses on a dataset from the north-east part of the field, which includes BHI images, cores, full 3D CT scans and conventional logs in four penetrations, three of which are horizontal, drilled through the faults; as well as 3D seismic data and relevant derived horizons and fault polygon interpretations. The available data have been investigated in detail, with all structural features in core, circumferential CT scans and BHI images systematically classified using simple and reproducible descriptive schemes. All the structural features have been orientated using directional data from BHI. The understanding of the character and fill of the fractures observed in core has also been incorporated. A further calibration with seismic and integration of results with information from previous studies allowed a full description of the fracture networks, of their densities within and outside the potential fault corridors of the studied field, as well as an assessment of their potential for reactivation and their possible impact on localised formation compaction. On the BHI images, several sub-vertical fractures have been identified, consisting mainly of mixed resistivity and resistive fractures, striking dominantly WNW-ESE. Particular zones along the wells have noticeably higher fracture densities, where features are organised in clusters; they are intercalated with zones where fractures are rarer. The clustering of fractures within fracture corridors are believed to be fault-related, subvertical and tabular fracture clusters that traverse an entire reservoir unit vertically and extend for several hundreds to thousands of feet laterally. These zones are believed to represent fracture corridors, which correlate with the structural lineaments observed on seismic. The fracture corridor network in the study area shows a variable deformation signature at the different scales of observations, but consists mainly of sub-vertical (dominantly >60°) deformation bands (c.50% of the features identified) and partially-cemented fractures (c.25-40%). Some of these features show a small displacement and it is believed this scaled variation in deformation within the corridors accounts for the overall larger, but relatively minor displacement observed on seismic (c.10-40ft vertical throw and possibly up to c.500m cumulative strike-slip observed in seismic).

fax 01-972-952-9435. AbstractGeosteering techniques are used to maximize exposure of well bore to pay zones. Accurate well bore placement is vital to the success of horizontal well drilling. The last 3 years has seen 50 horizontal wells drilled by PT Chevron Pacific Indonesia in the Central Sumatra Basin of Indonesia. We have found that geologic uncertainty is the largest risk to successfully drilling these wells. Small faults that cannot be accurately mapped with existing seismic and with displacements of 15 feet or less are commonly found and present a challenge to stay in the target. Obviously, the loss of objective section reduces the effective drilled lateral footage of a well and thereby affects productivity.One key to achieving desired lateral footage drilled is understanding the response of resistivity and gamma ray while drilling. That, combined with cuttings analysis, rate of penetration (ROP), and other drilling parameters, permits the response and reaction to geologic uncertainty to be managed more effectively. Monitoring these data as acquired in real time with reference to pre-job modeling, provides the key elements for intelligent decision making on trajectory decision. This paper will share specific examples of the challenges we have faced and how we recognize and react to geologic uncertainty while drilling.

An integrated geological study has been performed for a large, mature field at the Bekasap and Menggala formation. The primary goal of the study was to developed an integrated reservoir description for targeted infill drilling and improve recovery in a low-permeability reservoir. Integration of geological and petrophysical studies and reservoir performance analysis provided a rapid and effective method for developing a comprehensive reservoir description. A 3D geocelluar model of reservoir architecture and properties distribution was made and used as a guide to further development. This model delineates distinct trends of estuarine, sand ridge, and margin facies throughout the field that reflect paleogeography. Additionally, reservoir properties and saturations were geostatistically populated within the model. Horizontal wells were chosen as the preferred alternative to provide maximum exposure of reservoir layers and improve production and ultimate recovery compared to conventional vertical wells or frac jobs. Thirty one (31) horizontal wells were drilled in the Bekasap field, and this program was very successful and predicted ultimate recovery has improved from 14% to 28%. The study of this low permeability reservoir in the Bekasap field is an excellent opportunity to:demonstrate the economic importance of this zones,understand the methodologies required for identifying and evaluating these pay types, andhelp the company to find additional reserves in the Central Sumatra Basin. Introduction The Bekasap field is located at Sumatera Island, approximately 120 km north of Pekanbaru city, Indonesia, within Rokan Block Production Sharing Contract of PT. Chevron Pacific Indonesia (Fig-1). This field was discovered in June 1955, and put on production in September 1957, currently consisting of 107 producing wells, 16 injection wells, 12 P&A wells, and 2 disposal wells. Due to the long period of its production, most of the main reservoirs have shown pressure depletion. To augment the reservoir pressure and increase the oil production rate, the main reservoirs / high quality sands have been peripherally water flooded starting July 1997. The oil at the high quality sands that is referred to clean sands have been swept mostly by existing vertical wells, while low quality sands is refer to shally sands that have poor permeability but still quite potential in producing some oil contained in the sands. Cased hole resistivity has been run in several wells to identify the remaining oil left Following to the success of the pilot horizontal well Bekasap#103 in the low permeability reservoir, thirty one (31) horizontal was drilled. The targets of horizontal wells were 1950'Sand of Bekasap Formation and upper 2420' Sand of Menggala Formation. Generally, this program was very successful and delivered attractive improvement of ultimate recovery. However, several horizontal wells were recognized delivering oil below prediction due to any reason such as well placement, effective lateral length, drilling execution, and completion.

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fax 01-972-952-9435. AbstractAn integrated geological study has been performed for a large, mature field at the Bekasap and Menggala formation. The primary goal of the study was to developed an integrated reservoir description for targeted infill drilling and improve recovery in a low-permeability reservoir. Integration of geological and petrophysical studies and reservoir performance analysis provided a rapid and effective method for developing a comprehensive reservoir description. A 3D geocelluar model of reservoir architecture and properties distribution was made and used as a guide to further development. This model delineates distinct trends of estuarine, sand ridge, and margin facies throughout the field that reflect paleogeography. Additionally, reservoir properties and saturations were geostatistically populated within the model.Horizontal wells were chosen as the preferred alternative to provide maximum exposure of reservoir layers and improve production and ultimate recovery compared to conventional vertical wells or frac jobs. Thirty one (31) horizontal wells were drilled in the Bekasap field, and this program was very successful and predicted ultimate recovery has improved from 14% to 28%.The study of this low permeability reservoir in the Bekasap field is an excellent opportunity to: (1) demonstrate the economic importance of this zones, (2) understand the methodologies required for identifying and evaluating these pay types, and (3) help the company to find additional reserves in the Central Sumatra Basin.