CHRONOSTRATIGRAPHICALLY BASED RESERVOIR MODEL FOR CENOMANIAN CARBONATES, SOUTHEASTERN IRAQ OILFIELDS

  • Awadees M.R. Awadeesian Carbonate Stratigraphy Reservoir Development at Private
  • Sameer N.A. Al-Jawad Reservoir and Field Development Directorate
  • Salih M. Awadh Department of Geology, College of Science, University of Baghdad
  • Mjeed M. Al-Maliki Department of Geology, College of Science, University of Baghdad
Keywords: Chronosequence stratigraphy, Chrono-marker, Synchronous Layering, Sequence steering technique, Reservoir optimization

Abstract

The Cenomanian – Turronian sedimentary succession in the south Iraq oil fields, including Ahmadi, Rumaila, Mishrif and Khasib formations have undergone into high-resolution reservoir-scale genetic sequence stratigraphic analysis. Some oil-wells from Majnoon and West-Qurna oil fields were selected as a representative case for the regional sequence stratigraphic analysis. The south Iraqi Albian – Cenomanian – Turronian succession of 2nd-order depositional super-sequence has been analyzed based on the Arabian Plate chronosequence stratigraphic context, properly distinguished by three main chrono-markers (The maximum flooding surface, MFS-K100 of the upper shale member of Nahr Umr Formation, MFS-K140 of the upper Mishrif carbonates, and MFS-K150 of the lower Khasib shale member).
Three 3rd-order genetic mega-sequences were embraced between the cited chrono-markers. The markers have been considered as regional key-surfaces for the Late Albian – Cenomanian to Early Turonian and Late Turonian to Early Coniacian stratigraphy of the south Iraqi oil fields. Eight 4th-order genetic meso-sequences (MS1 to MS8) have been established, comprising multiple 5th-order high-frequency (HF) lithofacies cycles, successively arranged in the mega-sequences without disturbance. MFS-K135 (this study), MFS-K140, MFS-K150 and Seven successive regional chrono-markers [MFS-K120, MFS-K125 (this study), MFS-K130, and MFS-K160 of upper Khasib shale member] started from lower Ahmadi shale member, identify these meso-sequences. Associated fifteen key-surfaces (K121, K122, K123, K124, K125, K126, K127, K128, K129, K131, K132, K133, K134, K141 & K142) have been described as well. The meso-sequence 1 signifies Ahmadi lithofacies buildups, whereas; the other meso-sequences represent Mishrif lithofacies buildups. The Rumaila carbonates come across the first HST-unit of the meso-sequence 2. The meso-sequence 8 represents the Khasib carbonate facies buildups. The depositional super-sequence is terminated by type-1 sequence boundary SB-K150 at the top of the Mishrif Formation, created by maximum regression (MR). The study declares 15 reservoir syn-layers and 9 non-reservoir layers; each is essentially characterized by HF-single-lithofacies-cycle and lateral continuity pattern. This syn-layer model can be used as sequence steering technique for carbonates heterogeneity aspects, in the south Iraqi oil fields to control fluid dynamics in primary and secondary development projects.

Published
2018-11-27
Section
Articles