Ghazi Abdullah Al-Eid¹, Rami Ahmed Kamal², John C. Cole¹, Mahbub Hussain³, Geraint W. Hughes¹, M. Badrul Imam⁴

(1) Saudi Arabian Oil Company, Dhahran, Saudi Arabia
(2) Saudi Arabian oil Company, Dhahran, Saudi Arabia
(3) King Fahd Uneversity of Petroleum and Minerals, dhahran, Saudi Arabia
(4) King Fahd Uneversity of Petroleum and Minerals, Dhahran, Saudi Arabia

ABSTRACT: Identifying and Mapping Key Diagenetic Lithotypes; A New Approach in Modeling Carbonate Reservoirs

Thirteen key diagenetic lithotypes were identified from a study of thin sections taken at six-inch intervals along nearly one thousand feet of rock core recovered from eight deep wells that penetrated a heterogeneous gas-bearing reservoir interval in Late Permian shelf carbonates of the Khuff Formation in the subsurface of eastern Saudi Arabia.

The thirteen diagenetic lithologies existing today were traced back to three original parent rocks. The diagenetic pathways leading from parent rocks to offspring were charted and relative volumetrics established.

The diagenetic lithotypes were divided into two groups: non-reservoir lithologies (six) and reservoir lithologies (seven). The members in each group were then ranked as to their reservoir development properties; from best to absolute worse. Each lithotype was found to have its own characteristic porosity and permeability ranges.

The diagenetic lithotypes were color-coded and used to populate a high-resolution 3D geocellular model (vertical cell dimension: six inches) incorporating the study wells across the study area. Resulting patterns revealed colorful user-friendly sets of flow pathways, stratal relationships, and ancient depositional regimes. Potential is seen for using the system for more precise pore volume calculations.

The authors see the traditional complexities of diagenesis in ancient carbonates as becoming a user-friendly tool in facilitating the characterization of flow pathways in oil and gas reservoirs.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado