Abstract

This paper discusses case histories of more than sixty wells which requiredsand control. Approximately one half of the wells were gravel packed between1991 and 1994, with the remaining wells fractured stimulated (franc-packed!from 1992 through 1994. The case histories are as follows shallow gas fielddevelopment, geopressured oil and gas reservoirs deep gas reservoirs normalpressured as well as pressure depleted oil and gas sands. Included are bottomhole pressure transient testing results of fractured and conventional gravelpack completions. The resulting skin values and flow efficiencies from thetransient tests are discussed. Nodal analysis of completions comparing gravelacking to the fractured wells will demonstrate the improved productivityresponse realize. Cumulative production comparison will show the incrementalreserves gained, as well as accelerated reserve recovery due to decreasedrawdown and skin factors. Completions that were not perceived to becommercially viable with conventional gravel packing technology were attemptedwith this "frac-packing" technique and have proven to be not only mechanicallysuccessful but also commercially successful.

Introduction

High permeability fracturing has only recently become popular in sand controlenvironments(1,2,3). Little documented evidence exists other thantheoretical calculations and evaluations on productivity increases(4). This study describes a variety of sand control environments wherefracturing has been applied. Case histories will be described from shallow anddeep gas field developments and normal pressure (0.43 psi/ft) as well asgeopressured (above 0.6 psi/ft) oil and gas environments. Conventional gravelpacked completions arecompared to the fracture stimulated sand controlcompletions (frac-packs) within the same field. Finally, a summarizedcomparison of skin factors is presented with conventional ravel packcompletions versus the frac-packed completions.

Past attempts to compare these completion techniques have been eithertheoretical or extrapolated. Transient testing provides a direct measurement ofeach well's productivity, flow efficiency and skin(S) All transient testresults includedare from bottom hole data and not surface extrapolations hetransient information is then imported into a system analysis program todemonstrate the incremental productivity increases realized from frac-packcompletions as compared to gravel pack completions(6) In one casehistory, where bottom hole pressure transient tests from the original gravelpack ompletions are not available, a productivity measurement is ade based onsurface data.

Production decline curve data and cumulative production comparisons arepresented on wells which have been producing for more than one year. Thesedecline curve analyses indicate that the selection of a completion techniquedoes influence a well's flow rate and ultimate recovery. As a result of thesuccess of the frac-packing technique, some formations that were thought to benon-commercial were reevaluated nd incorporated into additional developmentlans.

Shallow Gas Development

Field Example No. I is a shallow gas field development with five frac-packedcompletions and twelve gravel packed completions. The reservoir is a dry gas, very unconsolidated sandstone from 1600 feet to 3900 feet with a pore pressuregradient of 0.468 psi/ft, reservoir temperatures of 112 degrees Fahrenheit andsand thickness varying from 4 feet to 2 feet, with offset development at thesame reservoir depths.

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