SEG Distinguished Instructor Short Course 2014

*A one-day course touring worldwide in 2014

Shawn Maxwell

Schlumberger

Microseismic Imaging of Hydraulic Fracturing: Improved Engineering of Unconventional Shale Reservoirs

Abstract

Hydraulic fracture stimulations are critical for the development of unconventional reservoirs, and the growing interest in shale reservoirs has resulted in the rapid expansion of microseismic fracture imaging. During high-pressure fluid injections of a hydraulic fracture treatment, microseismic emissions occur as cracks form and interact with pre-existing fractures. Images of the microseismic locations can be used to interpret hydraulic fracture geometries, including the direction, dimensions, and complexity resulting from networks of fractures in different orientations. The course will provide an overview of microseismic theory and practical application: from acquisition and survey design, processing through to interpretation. The emphasis will be on practical issues associated with acquisition of high-quality microseismic data, including potential pitfalls and quality control steps. Actual case studies will be used to demonstrate engineering benefits and improved production through the use of microseismic.

Who should attend?
The course is intended for geophysicists, engineers and geologists. The emphasis is on practical application and, as such, only basic prerequisite knowledge is assumed. The course would be most relevant to those currently involved with, or considering development of, unconventional reservoirs and particularly shales.

Course Objectives
Students will gain an understanding of the theoretical and practical aspects of microseismicity, including how to use data to improve engineering design of hydraulic fractures, as well as:

• Basics of hydraulic fracture operations
  
• Geomechanical processes that generate microseismicity, and how it relates to the hydraulic fracture growth
• Issues associated with high-quality microseismic data
  
• Common processing pitfalls and quality control approaches to processing workflows
• Identifying and accounting for potential monitoring biases
• Interpretation of microseismic images
• Application of microseismic data to fracture engineering challenges
• Monitoring-induced seismicity

Summary
The following topics will be addressed in the course:

• Introduction and History of Microseismic Monitoring:
  A review of the history of microseismic applications, including mining-induced seismicity, reservoir monitoring, and hydraulic fracturing for the stimulation of geothermal and oil and gas reservoirs. Practical application to engineering problems is stressed, including environmental concerns associated with the contamination of shallow aquifers and induced seismicity.
• Hydraulic Fracturing Basics:
  A tutorial of fracture mechanics theory, field operations and equipment, diagnostic technologies, and factors that influence hydraulic fracture growth. The review describes engineering challenges associated with designing an effective hydraulic fracture treatment ,and provides a context for practical application of microseismic imaging through the remainder of the course.
• Acquisition and Pre-Survey Design:
  Various microseismic monitoring configurations are described, including vertical, horizontal and multi-well downhole, surface, and shallow buried arrays. Pros and cons of each configuration are described along with acquisition system specifications and the impact on microseismic data quality. Essentials of survey design for both surface and downhole monitoring are given, along with criteria for designing an optimal monitoring system.
• Basic Processing for Microseismic Locations:
  Basis processing of microseismicity involves estimating the hypocentral location of the microseismic sources along with uncertainty estimates. A standard processing workflow is described, including velocity model construction and calibration. Standard location algorithms are described, with a focus on practical quality control. The impact of acquisition geometry on the resulting microseismic image is described.
• Geomechanics of Microseismic Deformation:
  Microseismic source characterization, including source strength estimates using magnitude scales and focal mechanisms, are presented. The relationship between deformations associated with the observed microseismic sources and the underlying hydraulic fracture are reviewed to provide context to interpret microseismic source characterization.
• Interpretation of Microseismic Fracture Images:
  Assessment of sensitivity, resolution, and confidence of microseismic images is reviewed. Workflows are described to remove potential biases and improve the accuracy of the microseismic events. Assessment of fracture direction, dimensions, complexity and stimulated volume from microseismic is described with a focus on interpretational pitfalls. Integration with other information is stressed to provide geologic and geomechanical interpretation frameworks.
• Engineering Applications of Microseismic Imaging:
  Presentation of case studies demonstrating various aspects of improving engineering designs for hydraulic fracture stimulations, well completions and field development. Various engineering design issues are discussed along with case study examples describing the use of microseismic data to improve the engineering design. The value of information considerations are described along with improving the economic viability of unconventional developments using microseismic imaging to increase productivity and reduce well, completion, and stimulation costs and designs using microseismic data.