No abstract

This reference is for an abstract only. A full paper was not submitted for this conference. In Kharir Field (Yemen, Block 10), major hydrocarbon accumulation is hosted in fractured basement. Along drilled basement sections, only restricted intervals account for flow. Accurate identification of open flowing fractures (amid numerous planar features) is crucial to characterize and monitor non-conventional basement reservoir. At well Kharir-XX, relevant logs were acquired in single run (Resistive-Acoustic Borehole Image, Fullwave Cross-dipole Acoustic, Induction and Spectral GR). Logging program was designed to provide maximal time for flowing intervals identification before decision to perform Formation Tester Run. Acoustic image and Cross-dipole full wave data acquired RIH were sent from wellsite, QCed and processed. Interpretation focused on Acoustic Travel Time Image which is a key parameter for flowing fracture recognition. Wellsite Monopole VDL images were used for evaluation of Stoneley Wave Reflectors. High-definition Array Induction Log and Micro-resistivity Borehole Imager data were logged whilst POOH and sent at regular intervals for evaluation. From above logs, fractures that appeared large, continuous and visible on the Acoustic Travel Time (potentially open at borehole wall); with a conductive appearance on micro-resistivity images were located and oriented. These fractures were then ranked taking into account their good match with while-drilling gas shows and increased rate of penetration. From tens of candidate intervals only twelve were selected for testing. Interval Formation Tester was deployed using Dual Inflatable Packer System (1m packer spacing). Borehole images were used to accurately position packers to avoid risking damage or no/lost seal. Formation Tester was run under Aphron mud system (reversible cake). Special clean fluid carriers inflated packers, thus avoiding risk of plugging fluid lines inside the tool with congealing mud. At well Kharir-XX, 80% of selected sampling stations gave reliable formation pressures, pressure transients, fluid gradients, mobilities and representative formation fluid samples.

The Dunbar Field (UKCS, Block 3/14a), operated by Total E&P UK, is situated on an intermediate terrace between the East Shetland Platform and the Viking Graben and characterised by a series of pre-Cretaceous and structurally aligned tilted fault blocks. The principal hydrocarbon accumulations are contained in the Middle Jurassic Brent Group and younger Upper Jurassic Heather Sands. Internally, the field is compartmentalised by a number of N-S faults and a secondary alignment of NE-SW faults which cross cut and often offset the main N-S faults. The larger scale faults down throw to the east and subdivide the field into four main areas; the West Flank, Central Panel and Frontal Panel with an uplifted Horst (Triassic) Panel in the south. Each of these panels has specific reservoir and fluid characteristics. The Central and Frontal panels have a substantial production history of 15 years. The field is in steep decline with high water cut in water flooded areas, and extremely low pressure in compartments produced by natural depletion. A better understanding of recovery from the main flow units is essential for estimation of drainage volume, optimisation of water injection pattern and infill well placement/completion. The ability to better define the size of the connected volumes through improved fault identification (Seismic PSDM3D Reprocessing) along with an improved understanding of the permeability field (sedimentological, petrographic, XRD, SEM, SrRSA, DST analysis & simulation studies) has been key in assessing Dunbar’s future potential. An intensive data acquisition campaign has been integrated in a comprehensive dynamic synthesis leading to a reservoir model history match that has improved our understanding of the field. This paper describes the multidisciplinary team work leading to an improved understanding of the recovery efficiency and reservoir connectivity leading to a further drilling campaign.