Abstract: “Physiographic Setting” refers to a geographic region influenced by unique climatic and other

environmental controls that impact shallow-marine carbonate deposition. At both a global and

local scale, physiographic setting should be factored into the exploration for most subsurface

carbonate plays. By doing so, the geographic areas for delineating prospective carbonate plays

are greatly expanded.

Physiographic setting at a global scale determines a basin’s proximity to the paleoequator and

whether carbonate deposition occurred in a tropical, subtropical or temperate climatic belt. The

climatic belt determines paleotrade wind directions and strengths and their potential influences

on carbonate play type. At a local scale, physiographic setting controls bottom topography (i.e.,

platform versus ramp, or something in between), which strongly influences carbonate facies

occurrence and distribution.

This talk will demonstrate the influence of physiographic setting on modern shallow-marine

carbonate platforms in the Bahamas Platform Complex, by contrasting styles of sedimentation

across the northern Great Bahama Platform with those across Caicos Platform in the southeast.

Our newer models from the windier Caicos Platform (strong easterly trade winds) expand the

potential for discovering high-energy facies (isolated reefs; oolitic and/or skeletal-oolitic

grainstones; leeward margin reefs) in areas not predicted by the established northern Bahamian

models. Further, the strong easterly trade winds shed more carbonate sand off the leeward

margins of Caicos Platform, producing pronounced onlapping wedges of grainstones. Thus,

many ancient leeward platform margins that were influenced by strong easterly paleotrade winds

may be prospective as well. Caicos Platform trade wind models have direct applications to

Phanerozoic subsurface shallow-marine carbonate sequences that were located between 5 and 22

degrees north or south of the paleoequator.

Caicos Platform models translate beautifully to lower and middle Cretaceous carbonate

sequences around the ancestral Gulf of Mexico Basin. During this time, carbonate deposition

occurred in a tropical belt 10-15 degrees north of the paleoequator, influenced by strong easterly

paleotrade winds. Those winds better explain the paleogeographic location of several large

carbonate pools whose settings were problematical, based on guidelines from the northern

Bahamas. These pools are: Black Lake Field in Louisiana (Sligo-aged; 156 MMBOIP); Fairway

Field in east Texas (Pearsall-aged; 410 MMBOIP) and the interrelated Golden Lane and Poza

Rica Fields in Mexico (Edwards-aged; >2 BBOIP for each pool). For each pool, I will show

how their geological attributes confirm that strong easterly paleotrade winds played a key role in

their initiation and evolution, consistent with the guidelines developed from Caicos Platform.

Bio: Jeff Dravis is a consulting carbonate geologist, primarily focused on aiding

in the discovery of oil and gas deposits, or enhancing their development once they are

discovered. He also conducts numerous applied training seminars for industry every

year.

Jeff received his Bachelor of Science degree in Geology from St. Mary’s University in

San Antonio, Texas. He obtained a Master of Science degree in Marine Geology from the

University of Miami’s Rosenstiel School of Marine and Atmospheric Sciences in Miami,

Florida. His thesis was entitled “Holocene Sedimentary Environments on Eleuthera

Bank, Bahamas.” Jeff then entered Rice University, Houston, Texas, to begin work on

deep-water carbonates under the direction of Dr. James Lee Wilson. He was awarded a

Ph D in Geology; his dissertation was entitled “Sedimentology and Diagenesis of the

Upper Cretaceous Austin Chalk Formation, South Texas and northern Mexico.”

Dr. Dravis began his professional career in Houston with Exxon Production Research

Company. There, he conducted applied research on carbonate facies, diagenesis and

porosity evolution, but also headed up Exxon’s worldwide training efforts in carbonates.

This training included teaching in-house seminars, as well as leading combined modern

(Bahamas and Florida) and ancient (Texas and New Mexico) carbonate field seminars for

the corporation.

In 1986, Jeff started his own consulting practice in Houston. First, he founded

Dravis Interests, Inc. to provide technical expertise and training in applied carbonate

petroleum geology to the oil and gas industry. Later, Dravis Geological Services was

created to handle all technical consulting projects. Jeff has completed 195 technical

projects worldwide, working on carbonate sequences ranging in age from Cambrian to

upper Tertiary. He has presented 310 in-house and field seminars to industry, both on a

public and private basis, including 73 seminars to Caicos Platform in the southeastern

Bahamas and numerous ancient field seminars to west Texas and New Mexico. His

training clients are domestic and foreign oil companies, both majors and independents.

Jeff is an Adjunct Professor of Geology at Rice University. Since 1987, he has taught

parts of graduate courses, taken students into the field, and served on thesis committees.

Starting in 2016, he began teaching the carbonate geology segment of the University of

Houston’s Professional Master’s Program in Petroleum Geology, and just finished his

fifth segment in mid-September.