Shale Gas Production Analysis, Phase 2Completed

Investment:

$42k (USD) per Sponsor

Status:

Completed

Principal Investigator(s):

The key to the identification of prospective shale gas plays and to the development of enhanced production and simulation technology is an understanding of the production mechanisms. In turn, this hinges on the availability of a model of the production process that represents the physical aspects of the reservoir and the completion and provides a satisfactory match with available production data.

Gas production models for shales have been developed over the last 50 or so years, based on models for the production of gas from coal beds and applied initially to low pressure fractured shale reservoirs such as the Antrim and Devonian shales. There is now a plethora of numerical models and semi-analytic models available that are applied to higher pressure shale reservoirs such as the Barnett and the Haynesville, but are still based on an understanding of the production process in the low-pressure shales.

The objectives for Phase 2 are to use the newly developed model from Phase 1 and the understanding gained from our Phase 1 analysis to:

  • Refine and enhance the production data analysis and production prediction software tool developed as a prototype in Phase 1
  • Collect and analyze publicly available production data for several shale plays
  • Analyze sponsor-supplied production and completions data (when available)
  • Develop correlations for “completions production coefficient” with completions parameters, such as perforated length, number of stages, and lbs. proppant pumped
  • Develop a better understanding of the impact of completions processes and ultimately provide a better definition and identification of “sweet spots”
  • Propose estimates for the effective drainage area of a well,  to provide better estimates of recovery factors, well spacing and well interference
  • Critically assess industry perceptions of factors that may or may not impact shale gas production
  • Explore the applicability of the concepts that were developed during Phase 1 for shale gas production to shale liquid production. We further propose to investigate the applicability of that modeling process to shale oil reservoirs.

Phase 2 focuses on developing further several of the issues that arose from our Phase 1 investigation.

As we outlined at the start of Phase 1, the key to the identification of prospective shale gas plays and to the development of enhanced exploration, production and stimulation technology is an understanding of the production mechanisms. In turn, this depends on the availability of a model of the production process that represents the physical aspects of the reservoir and the completion and provides a satisfactory match with available production data.

To address these issues, we developed in Phase 1 a method of modeling and analyzing production data from shale gas wells and plays that combines the ease and simplicity of use of conventional decline curve analysis while at the same time honoring and identifying the essential physics of the process. Features of this new technique include:

  • A method of presenting and analyzing production data that has allowed us to propose and evaluate an alternative metric for shale gas productivity—the Production Coefficient.
  • Identification of the primary determinants of shale gas productivity and the demonstration that only a specific combination of these parameters (that together constitute the Production Coefficient) can be obtained from history matching.
  • Insights into the role of natural fractures in the production process.
  • The role of completions, stimulation and production parameters in determining well productivity.
  • The reservoir and geologic parameters that are the primary determinants of productivity and therefore should be used (as a group) to identify “sweet spots” within plays.

In Phase 2 we have used the semi-analytic production model developed in Phase 1 and the understanding gained from it to:

  1. Better characterize shale gas production through various stages of production including early-time transient (influenced by variable drawdown), linear flow and boundary-dominated flow. This involves the development of an improved asymptotic model and an improved (and unique) method of data interpretation, leading to better forecasts of EUR, particularly with limited production data. Industry interpretation of the restricted choke technique will be critically assessed.
  2. Improve understanding and application of decline rates and decline curve analysis; this will include a critical assessment of industry perceptions and use of decline rate and decline curve analysis.
  3. Provide an estimate of stimulated reservoir volume and productive reservoir volume. We will develop a method of identifying well-to-well interference and assessing its impact on well productivity. We will provide guidelines as to appropriate well-to-well spacing.

We also extend the semi-analytic shale gas production model developed in Phase 1 to shale liquids production.

Results

Several issues that were raised in Phase 1 have been developed further in Phase 2 of the project. We have focused on four main topics as outlined below.

  1. Improved Interpretation of early-time data: a better asymptotic model
  2. Decline Rates and Decline Curve Analysis
  3. Shale Oil Production Analysis
  4. Optimal Well Spacing and Well-to-well Interference for Shale Gas Reservoirs