A Holistic Approach to the Development Stage of Shale Gas Resources
Authors: Navarette Mike , Chorn Larry , Maucec Marko 
Published: May 2016

Source rock reservoirs (SRRs) are found in conventional oil and gas basins. The development of a SRR depends on the geological, geochemistry, petrophysical, and geomechanical parameters, as well as economic constraints in the targeted area. While SRR exploration and appraisal methodologies are fundamentally different from conventional assets, the development stage takes on more similarities to conventionals. However, conceptual differences remain that require technical professionals and managers to alter time-tested approaches. Unconventional SRRs impose significant engineering constraints because reserves are spread across large compartmentalized stacked or layered reservoirs, which are highly heterogeneous and contain wide ranges of mineralogy. This paper is a continuation of the exposition on a holistic approach to shale gas and oil development, which has been developed in detail and encompasses more than 25 years of service company experience in US gas shale plays (Navarette et al. 2013a, 2013b).

The objective of this work is to provide a guideline for acquiring and applying a better understanding and application of SRR reservoir quality and deliverability insights. The goal is to position geoscientists and engineers to maximize well productivity, improve hydraulic fracturing stimulation effectiveness, and optimize drilling and completion efficiency. This paper identifies critical paths and key technical elements or tasks associated with SRR field development. Previous data (seismic, logs, cuttings, mud logs, extended production tests, and optimized well construction and stimulation practices) acquired in the Screening and Appraisal stages are used. A methodical approach is presented that addresses the following key tasks:Categorize critical SRR attributes and key learnings.Confirm hypotheses tested in the Appraisal stages.Establish drilling program plans for the best reservoir targets (sweet spots) with well location and lateral orientation.Maximize the stimulation potential and recovery factor.

This work provides a proven road map for the evaluation and development of SRRs. Critical paths with the associated key technical elements address and provide a project scope of challenges, which enables a holistic solution to successful unconventional SRR development.

Introduction

Currently, organic-rich, fine-grained source rocks are the target of intense exploration and drilling for natural gas. So-called thermogenic shale-gas reservoirs comprise a new and abundant type of unconventional energy resource and are commonly referred to as SRRs. SRRs are characterized as Type 3 petroleum systems that have a much lower permeability and much smaller pore throats compared to conventional petroleum systems (Type 1) or even continuous basin-centered accumulations (Type 2). The remaining unexpelled and unmigrated hydrocarbons that remain in the porosity of the SRR can be produced if sufficient fracture conductivity is induced by hydraulic fracturing. Coalbed methane (CBM), oil sands, and oil SRRs are variations on, and composites of, the three basic petroleum systems end members (Williams 2013). The hydrocarbon reservoir type classification is presented in Fig. 1.