This paper presents a new structural model for the North Kuwait Carbonate fields as well as its implications in term of fracture modelling and field development. It also describes a workflow which can be used as foundation for further fracture modelling study at production and exploration scales alike. This workflow consists of a four step approach: 1) elaboration of a regional structural model, 2) creation of 3D conceptual fracture diagrams, 3) elaboration of constraints capturing the key elements of the conceptual diagrams and 4) creation of fracture model properties for further dynamic simulation. The application of this workflow resulted in the creation of a series of fracture models for the North Kuwait Carbonates fields. During the first step of the study, a new structural model has been elaborated based on key kinematic observations from well and seismic data, as well as experimental and field analogues which have been linked to the known regional phases of deformation. These main phases of deformation are 1) post Triassic rifting, 2) Alpine 1-late Cretaceous transtension and 3) Alpine 2-Mid Tertiary compression related to the Zagros formation, which has the greatest impact on the formation of the pre-Gotnia structures and fracture development. The major difference between the new model and previous structural thinking is that the formation of the compressional folds in the Carbonate fields (an event that shaped the current outline of the fields) has happened during the Tertiary time instead of Jurassic time. The proposed structural evolution has been used to define characteristic structural domains. These structural domains have defined a foundation to elaborate conceptual fracture diagram to support fracture modelling study work. The fracture conceptual models have potential implications on fracture development and preferred direction of horizontal and deviated wells. Greater fracture connectivity is expected in compressional ridges developed in Tertiary time, while in the area between the compressional ridges, less dense fractures and probably more cemented fractures (likely to have developed before hydrocarbon emplacement) are expected. The new view on the timing of the structural development (i.e., late uplift of compressional ridges regionally) also has possible implications on maturation/charge history as well as reservoir properties development. The new proposed model for structural evolution is now being used as a foundation for appraisal and fracture modelling activities of the pre-Gotnia carbonate reservoirs. A fracture characterisation study integrating all available static and dynamic data is ongoing.

The North Kuwait Carbonate (NKJG) reservoirs are currently under development by KOC (Kuwait Oil Company). The appraisal and development of the NKJG offer challenges such as lateral variations in reservoir quality, tight to very tight reservoirs and natural fracturing to a varying degree spatially. The presence of open, connected fractures is one of the key elements to achieve a successful development. Also, the presence of fracture corridors increase the risk associated with drilling. Numerous fracture modelling studies have been supporting both appraisal and development strategies of the fields. A structural evolution model has been developed based on field observations and linked to the regional phases of deformations. Detailed fracture characterization using static BHI (bore hole images) and core data as well as dynamic data has been achieved. Small scale detailed DFN (Discrete Fracture Network) in support of planning and drilling activities of future appraisal wells has been carried out. Full field DFN in support to production history matching and forecast has been completed. The core and pressure transient analysis data have been used to calibrate the permeability and porosity of the DFN property ahead of the dynamic simulation work. This paper illustrates some examples of best practices of the various study components with a focus on core to BHI calibration, fracture porosity calibration using core data and calibration of DFN models using pressure transient analysis data.

The North Kuwait Carbonate (NKJG) reservoirs are currently under development by KOC (Kuwait Oil Company). The appraisal and development of the NKJG offer challenges such as lateral variations in reservoir quality, tight to very tight reservoirs and natural fracturing to a varying degree spatially. The presence of open, connected fractures is one of the key elements to achieve a successful development. Also, the presence of fracture corridors increase the risk associated with drilling. Numerous fracture modelling studies have been supporting both appraisal and development strategies of the fields. This paper illustrates how small scale detailed DFN (Discrete Fracture Network) can support the planning and drilling activities of future appraisal wells. A series of detailed DFN models has been built around existing wells. The DFN models are based on a thorough structural understanding, detailed fracture characterization using bore-hole image (BHI) and core data around the wells of interests. In addition to the fracture characterization work, mechanical stratigraphy has been elaborated using E-facies and geomechanical logs. Fracture connectivity analysis has been carried out to calibrate the DFNs to the static and dynamic well data. Scenarios of DFN models can now be used to communicate with drilling in order to illustrate the potential fracture corridors distribution in the sub-surface.

The North Kuwait Carbonate (NKJG) reservoirs are currently under development by KOC (Kuwait Oil Company). In addition to the matrix heterogeneity, natural fracturing poses extra challenges for the optimization of the field development planning. The presence of open, connected fractures presents opportunities for infill drilling but increases the risk of water invasion and drilling related issues. Numerous fracture modelling studies have been supporting both appraisal and development strategies of the fields. The translation of the field observation and detailed fracture characterization using static BHI (bore hole image) and core data yields a series of geological concepts. These concepts capture end members of the spatial distribution of the major conductive features and provide a range of realizations for the geometrical extent of the fracture zones. Given the large uncertainty in the dynamic properties of the fracture; pressure transient analysis (PTA), complemented by core data, has proven to be key in narrowing the range of fracture equivalent permeabilities and porosities that are carried forward in the history matching step. This paper focuses on illustrating the integration of different aspects of Pressure Transient Analysis data to pre-condition the discrete fracture network (DFN) model realizations. Comparison between KH from well test and log data allows to discriminate fractured from matrix wells. Dedicated sector models around fractured wells are built to assess the impact of the matrix, faults and fracture properties on the transient pressure response. Numerical simulations are conducted directly on the static model with the fractures explicitly captured as discrete surface features. For each DFN configuration, a sensitivity analysis of the fracture properties is performed and the characteristics of the resulting pressure derivatives are then compared against the well test data to select the plausible realizations that honor both geological and flow data. In this paper, a series of examples demonstrating the application of the methodology are presented for different areas of the field.

Fracture characterization is vital for efficient field development of naturally fractured Carbonate reservoirs. Successful development of fracture reservoir in the study area was possible due to early recognition of fracture play right from the exploration phase and through careful execution of relevant data acquisition campaign in the initial stages of field development. Comprehensive and integrated studies have been carried out over the past few years to arrive at an understanding of the conceptual model in deciphering structural evolution of North Kuwait Jurassic.Extensive core and image log data was acquired in the initial stages of field appraisal, which helped in comprehensive forward planning in design of deviated and horizontal wells. The data analysis steps included accurate and reliable reorientation of the cores. These data were calibrated with the image logs, along with available seismic attributes, which resulted in better understanding of structural evolution and sweet spotting of horizontal wells. This reorientation of the core data also helped in establishing a number of quantitative fractures attributes such as frequency, spacing, dip-azimuth and aperture along with mapping of in-situ stress directions. The detailed integration of these data also helped in accurately mapping the local and regional present day stress and its variations spatially across the fields. Stress direction across the field was helpful for deciding the azimuth of wells during well planning along with selection of completion strategy for current set of horizontal drilling Campaign.Drilling and testing results have been encouraging through enhanced reservoir performance in these tight carbonate reservoirs, based on these integrated studies.