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Development ofthe ShearwaterField, adeepgas-condensateaccumulation inthe HPHT region ofthe UKCS, beganin1997 withthe initiation ofdevelopment drillingandconstruction oftopside facilities. Itformed part ofthe major development ofthe CentralNorthSea HPHT gasplaythroughoutthe late1990s,togetherwith othergasdevelopments across Elgin/FranklinandE rskine.Ass uch, Shearwaters houldb eviewed, together withtheseotherstructures,aspart ofanexpansion ofthe gassector int he NorthSea inanarea ofchallenging subsurface conditionsandlimited development experience to constrainp roduction uncertainty. Fieldsanction wasbased on the understandinga ndmodellingofk eys ubsurface uncertainties. Development experience since thenhast ested thatinitials ubsurface viewandlessons learnt will provide ak eyanalogueto help constrain the development ofa ny futureH PHT gasaccumulations. Thisp aperdescribest he subsurface modelfor the Shearwaters tructurea ndh ow recent development experience andproduction performance hasconstrained the reservoircharacterization uncertainty ofthe FulmarFormation.DVD: CoredisplayD1isr elevant to thischapterandcanbe viewed on the accompanyingDVD.The ShearwaterFieldrepresents anintegralp art ofthe recent development ofthe CentralNorthS ea high-pressure/hightemperature(HPHT)p etroleum system,providingb othg ascondensatef rom its Jurassic reservoirs anda lso aprocessingh ub facility for neighbouringd evelopments. Located 250kmeast of AberdeeninBlock 22/30b ( Fig.1 ),the fieldwaso riginally discovered in1 991byexploration well 22/30b-4re, which encountered richg as-condensateh ydrocarbons atr eservoir pressureso f15100 psia tt he crest ofthe structure.Subsequent appraisalin1 992 (22/30b-11) and1996 (22/30b-15s1) further confirmed the presence ande xtent ofac ommercialv olume, sufficient for fieldd evelopment sanction in1 997. Drilling constraints associated withsubsurface HPHT conditions,together withsignificant concerns regardingthe ability to drill into a partially depleted reservoir,meant thatall ofthe development wells needed to be drilled vertically inthe reservoirandbeforefirst gasw asp roduced.Ino rdert os atisfyt hesefi eldd evelopment constraints ac omprehensivereviewo fsubsurface uncertainties anddevelopment options wasundertaken. Thisformed the focus of the initialfieldgeologicalmodelling, constrainingthe numberand placement ofd evelopment wells andtheircompletion interval (Blehaut etal .1 999). Asix-well drillingc ampaignfollowed, between1997 and1999,beforeinstallation ofthe platform facility in2 000. Fivewells weretargeted att he FulmarFormation,with the remainingwell havinga nappraisalelement to test structural definition att he crest ofthe field(to distinguishb etweent he wedge, monoclinea ndslump models ofB lehaut etal .( 1999)). Thisappraisalw ell encountered ag as-condensateP entland Formation section andproved astructurec omparableto the wedge modelofB lehaut etal . ( 1999).Drillinga fterp roduction start-up wasalways considered unlikely becauseofthe riskst oholestability. However,awell failureresulted...

A new solid-state, high-resolution acoustic imaging technology has been applied in hydraulically fractured wells to image and quantify perforation erosion. The downhole device captures detailed full-lateral logs of horizontal wells, without the need for clear fluids to facilitate measurements. This paper discusses how the imaging technology functions, lab testing that validated the measurements, and field testing completed with several operators in a variety of reservoirs and basins. This high-resolution, acoustic-based downhole imaging technology provided a 360-degree view inside a variety of wells. Instead of optics, the imaging technology used high-frequency sound waves to image a full lateral through opaque fluids at sub-millimetric levels. The imaging tool was conveyed on either tractor or e-coil to continuously log the wellbore between 15 and 30ft/min, completing a full azimuthal scan that imaged individual perforations regardless of orientation. A range of imaging techniques quantified and measured each perforation to determine the extent of erosion in each perforation, cluster, and stage sustained during the hydraulic fracturing process. The acoustic imaging technology was initially tested in the lab with calibration jigs and perforated pipe samples to validate its accuracy. The technology was then field deployed by several operators and used to assess perforation erosion in extended horizontal wells by scanning the entire well from toe to heel and measuring thousands of perforations in a single log. The data gathered quantified the perforation diameter, perforation erosion range, perforation orientation dependency, cluster efficiency, perforation erosion bias, and discovered the presence of significant casing damage around areas where plugs were set. The image results showed the distribution, size, and measured diameter for each perforation in each cluster. The results noted toe or heel biases and how these changed in different well types and designs in different basins. The data allowed operators to reach conclusions regarding erosion and cluster efficiency across the entire lateral in various wells in the Montney, Permian, and Anadarko basins. Wells across North America were scanned in several other basins for comparison purposes using various completion designs from different operators. The high-resolution acoustic imaging technology offers a robust 360-degree view of long horizontal wells and perforation measurements post-fracture. Over 35,000 perforations have been measured using the technology in the field across various well types with different designs. The technology has proven to be a valuable tool in improving and optimizing completion designs by providing detailed feedback on where designs are working effectively and where they can be improved.