Formulation of Appraisal Strategy and Process Workflow for Testing the Deep Unconventional Oxfordian-Callovian Age Reservoir of North Kuwait: A Case Study

Abstract

Kuwait Oil Company is currently engaged in an early phase of appraisal of the deep tight fractured carbonate reservoirs and resource plays in the northern part of Kuwait, as part of the strategy to meet the long term gas production targets. The operational area in northern part of Kuwait encompasses approximately 1800 sq.km covering eight Oil & Gas fields. These unconventional reservoirs of Oxfordian – Callovian age with very low permeability (typically less than 0.01mD), occurring at depth range of 14000’ – 15000’ comprise naturally fractured tight carbonate reservoir unit (average 45’ thickness) overlying organically rich (Kerogen) resource play unit (average 50’ thickness) which is underlain by a unit (average 40’ thickness) consisting of alternations of tight limestone and organically rich argillaceous layers.

These unconventional reservoirs are immediately overlain by the very highly over pressured (up to 21 ppg mud weight equivalent) Kimmeridgian - Tithonian age Hith-Gotnia Evaporite formations (Anhydrite + Salt alternations) which act as the regional top seal and also pose severe constraints in the well design , placement and completion of the horizontal appraisal wells.

Incorporating the data obtained from about 120 vertical / deviated well penetrations, comprehensive and integrated collaborative multidiscipline studies have been carried out over the past few years leading to very good understanding of the Structural evolution of north Kuwait structures and robust Sedimentological & Sequence Stratigraphic models for these reservoirs. Based on these studies an Appraisal Strategy has been formulated which has been Peer reviewed incorporating the identified Key Enablers, Critical Success Factors , Sweet spots leading to generation of Conceptual Risk Segment Map for locating the prioritized Horizontal appraisal wells with customized Well Completion. In addition, a new process work flow has been introduced for achieving improved synergy and integration of diverse data sets in one common platform leading to effective decision making and optimization with regard to well perforation and testing recommendations resulting in improved well delivery.

This paper discusses the appraisal strategy, significant success and the lessons learnt from the 6 Horizontal appraisal wells drilled in the north Kuwait area targeting these unconventional reservoirs.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018