PBS-SEPM 2021 November Luncheon - Dr. Robert Lindsay

"Requisites of Cementation and Dissolution"
 
Presented by Dr. Robert Lindsay at the November Luncheon Meeting of the Permian Basin Section-SEPM
Tuesday, November 16, 2021
 
ABSTRACT:  Requisites of cementation and dissolution are: 
Source of Ions or Lack of Ions 
Pipeline 
Pump 
Precipitator or Dissolver 
Time 
1. Source of Ions or Lack of Ions (Sw): Refers to the water chemistry that passes through porous strata (unconsolidated sediment to lithified rock). These fluids can be of variable composition, from: 1) sea water; 2) fresh water; 3) brackish water; 4) evaporitic water; or 5) subsurface brine. Source of these fluids is the hydrologic cycle that continuously refreshes earth with water. 
 
2. Pipeline (ф): Refers to porosity fairways, faults, and fractures that fluids flow through. 
 
3. Pump (↑ pressure → ↓ pressure): Refers to the head of energy that drives fluids through porous strata. Fluid flow is from high pressure to low pressure. Examples are: 1) structural relief; 2) fault movement; 3) gravity; 4) subaerial exposure; 5) mechanical and chemical compaction; 6) rivers; 7) waves; and 8) currents. 
 
4. Precipitator or Dissolver (↑ Sw or ↓ Sw): Refers to fluid flow reaching supersaturation or undersaturation as it passes through porous strata in the pipeline (catalyst). 
 
5. Time: Associated with these processes is time, a long-term issue. If drawn out over long periods of time, intervals of strata can have multiple fluid chemistries pass through the pipeline to: 1) reduce porosity and permeability; 2) create or preserve porosity and permeability; or 3) repeat these processes again and again.
 
These processes can either: 1) create cement, which reduces total porosity and associated pore throat widths to reduce permeability; or 2) create or preserve porosity, which increases or preserves pore throat size and associated permeability.In the final analysis, porosity is where water, oil, gas, brines, and minerals reside or are emplaced. These requisites are a simple and straight forward way to view the complexity of diagenesis that affects strata through time.