The Effect of Strawn (Desmoinesian) Paleogeography and Paleolatitude on the Distribution of Carbonate Facies in the Byrant G Field, Midland Basin, Texas

Abstract

Paleogeography and paleolatitude reconstructions assisted in locating Strawn Formation grainstone shoals that form a stratigraphic trap on the eastern edge of the Byrant G field. Previous to this study, Strawn production was thought to be limited to fractured mudstoens found predominantly in the northwestern parts of the field. The grainstones were tested by a recompletion adding prolific new pay in the Strawn. The Desmoinesian paleolatitude and paleogeography of the basin influenced carbonate sedimentation at the Byrant G field by controlling the direction of regional prevailing winds and ocean currents. Wind directions change in relation to latitude. When within 10{degree} north or south of the equator, prevailing winds generally are northeast or southeast, respectively. Because the Midland basin was very near the equator during the Desmoinesian, sedimentation at the Byrant G field would have been influenced by winds and currents from a southeasterly or northeasterly direction, depending on paleolatitude. Grain dominated sediments were predicted to accumulate on east-facing edges of structural highs because the Desmoinesian prevailing winds and ocean currents generally were easterly. Indeed, grainstones were located on the eastern or windward edges of structures in the field. They probably were deposited as beaches or marine shoals oriented slightly northeast-southwest. Furthermore » to the west, gray mudstones, representing leeward deposits, accumulated in what probably was a lagoonal environment. These facies changes indicate an environmental transition from high to low energy in an east to west direction across the field.« less