ABSTRACT: Petrophysics to Geophysics--Matagorda Island 519 Field, Interrelating Attributes

BROWN, ALAN LEE, Amoco Production Co., Houston, TX, and RICK LINDSAY, Amoco Research, Tulsa, OK

The Matagorda Island 519 field is located in the lower Miocene clastic growth fault trend of offshore Texas. The trapping structure is a rotated normal fault block with updip thinning of the main Discorbis bolivarensis reservoir. Sediment deposition of the main reservoir unit took place rapidly along an unstable shelf margin. Overall, the reservoir sequence is a coarsening-upward shelf bar facies capped by a thinning upward, rapidly transgressing marine sequence. Delineation of pay and nonpay stratigraphic intervals by differentiating subtle wireline log and seismic amplitude response variations is the primary objective of the study. An integrated approach combining geological/petrophysical data from wireline logs, cuttings, and core was used to develop geophysical models related to i situ reservoir rock and fluid conditions.

Investigation of two cores from two wells out of the five penetrating the reservoir unit indicate that: (1) small grain size variation between good and poor reservoir rock in the upper fine-grained to silt-sized range; (2) quartz content was high in the good quality reservoir and low in the poor quality section; (3) abundant k-feldspar throughout the section was the main control on the gamma ray log response; and (4) pay zones are best defined by a combination of Buckles and Production Ratio Index plots. In addition, techniques were established for relating lab measured rock properties for compressional velocity, shear velocity, and bulk density estimates to in situ measurements of sonic log compressional velocities and bulk density log data used in geophysical modeling.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)