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WTGS December 12, 2017 Luncheon meeting

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Date/Time
Date(s) - 12/12/2017
11:30 am - 1:00 pm

Location
Midland Country Club Upstairs Ballroom

Categories


Hybrid Model of Dolomitization

Permian Basin

Robert F. Lindsay

Lindsay Consulting & Brigham Young University

Midland, Texas & Provo, Utah

 

A hybrid model of dolomitization is responsible for dolomitization of Permian carbonate strata via: 1) reflux-mechanical compaction dolomitization during the Permian; and 2) tectonic, topographic driven and hydrothermal dolomitization during the Late Eocene to Early Miocene. The end-product was massive dolomitization of Permian ramp/shelf carbonate strata surrounding the Permian Basin and enhancement of porosity-permeability via improved connectivity. Improved connectivity modified conventional reservoirs throughout the Permian Basin so that they would waterflood more efficiently. The down side is that residual oil zones (ROZ’s) were developed.

Reflux-Compaction Model:

Study of >3000 thin sections and >150 cores revealed that dolomitization of Permian strata was during initial burial as strata experienced mechanical compaction. Dolomitizing brine was sourced from a distant, broad, inner ramp lagoon-intertidal environment. During burial, Mg2+ rich brine was expelled by mechanical compaction to dolomitize down-dip carbonate strata. Proof was mechanical compaction of grains and mud prior to lithification by dolomitization and is herein called the reflux-mechanical compaction model of dolomitization.

Dolomitization formed cloudy, inclusion-rich, E-planar, highly etched dolomite. Porosity was preserved in grain-rich strata, with additional porosity created as the brine became depleted with Ca2+ and CO32-, with partial dissolution of carbonate grains during dolomitization.

Relative sea level fluctuations during late highstand–early lowstand restricted the inner ramp to form Mg2+ rich brine favoring density-driven circulation of brines. However, inner ramp strata are 1.25-3+ times wider than down-dip carbonate strata, which brings up a problem as to the speed with which brine could move from up-dip to down-dip.

The reflux-mechanical compaction model of dolomitization provides a better and more efficient way to deliver and distribute dolomitizing magnesium (Mg2+) rich brine from regional up-dip inner ramp/shelf anhydritic dolostone and evaporite strata to down-dip carbonate ramp/shelf margins.

Key points of the Reflux-Mechanical Compaction Model are:

  • Active during initial burial to shallow burial
  • Hypersaline inner ramp lagoon-intertidal environment concentrated Mg2+

Concentration was by surface evaporation of seawater

5° N latitude

  • Brine density gradient and gravity flow provided an initial push down-dip
  • Mechanical compaction provided an overall push down-dip
  • Dolomitization was fabric preserving
  • Dolomite crystals

Fine crystalline

E-planar

Tectonic, Topographic Driven and Hydrothermal Models:

During the Late Eocene-Early Miocene, uplift formed the Southern Rocky Mountain Epeirogen (SRME) and initiated the Rio Grande Rift (RGR) via crustal heating as intrusive plutons and extrusive volcanism formed the Trans-Pecos magmatic province and larger North American Cordilleran alkali igneous belt.

By 38-35 Ma an erosional surface extended across New Mexico to form an immense recharge area into the Permian Basin. Meteoric water heated to 113°-224° C by contact with plutons. During recharge, undersaturated meteoric water partially dissolved Permian dolomite and precipitated clear, inclusion-poor, E-planar, limpid dolomite cement. Area of meteoric recharge was 130 miles (209 km) wide and partially to completely swept Permian Basin oil fields of primary and secondary recovery oil to residual oil saturation to waterflood (Srow), forming residual oil zones (ROZ’s).

Extension of RGR, during Middle-Late Miocene, destroyed the massive recharge area and allowed oil columns to partially to completely resaturate with oil or gas.

Key points – Tectonic, Topographic Driven and Hydrothermal Models:

  • Regional uplift was created by emplacement of plutons-volcanics
  • Hot fluids were expelled from crustal sections by tectonism (metamorphism and igneous intrusions)
  • Active in the uplifted western basin margin of Permian Basin
  • Created massive volumes of meteoric recharge into the subsurface
  • Plutons heated meteoric recharge fluids
  • Fluid flow was through aquifers-reservoirs
  • Fluids recrystallize existing dolostones
  • Magnesium (Mg2+) was concentrated by partial dissolution of Permian dolostone strata
  • At saturation, limpid dolomite cement precipitated
  • Dolomite crystals are E-planar, highly etched, inclusion-rich and inclusion-poor

 

Robert (Bob) F. Lindsay

Born and raised in Utah (United States)

    • Served in U.S. Army Special Forces, known by their nick name “The Green Berets”Graduated from:Weber State College 1974 – B.Sc. Geology

      Brigham Young University 1976 – M.Sc. Geology

University of Aberdeen 2014 – Ph.D. in Geology

Bob has worked for:

      1. Gulf Oil, 1976-1985, Production Geology, Enhanced Oil Recovery (Supervisor EOR Geology), and Applied Research
      2. Chevron, 1985-2001, Carbonate Petrographer, Laboratory Supervisor, and Stratigrapher
      3. ChevronTexaco, 2001-2002, Carbonate Specialist
      4. Saudi Aramco, 2002-2015, Geological Specialist, Geological Consultant, Sr. Geological Consultant (Geological Technical Services Division), Carbonate Sedimentology and Sequence Stratigraphy, leading Aramco carbonate field trips and teaching graduate level carbonate sedimentology at King Faud University of Petroleum and Minerals (KFUPM)
      5. Lindsay Consulting LLC & Affiliated Faculty Brigham Young University, 2015-Present, Consulting on Permian Basin oil fields, leading field trips, teaching graduate level c
      6. ourse “Rock-based Integrated Reservoir Characterization” and short courses

Bob has served as:

      1. Editor for Oklahoma City Geological Society (1980-1982)
      2. Co-chairman and Chairman SEPM Evaporite Research Group (1984-1986)
      3. A Distinguished Lecturer (1993-1994) American Association of Petroleum Geologists
      4. President Permian Basin Section – SEPM (1994-1995)
      5. President West Texas Geological Society (2000-2001)
      6. Executive Committee Member – Dhahran Geoscience Society (2005-2007)
      7. Distinguished Lecturer (2013-2014) Dhahran Geoscience Society

He has published 104 abstracts and papers

Bob spends his retirement time giving back to academia and industry by:

      1. Running field trips, giving talks and teaching short courses for geological societies, universities and industry
      2. Teaching at Brigham Young University

He and his wife Linda have 5 children and 18 grandchildren

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