Buried Arrays

The Buried Array is an innovative and unique microseismic monitoring method invented by MicroSeismic, Inc. It is the ideal solution for operators who need to monitor the hydraulic fracturing of multiple wells over a larger area, and over a longer period of time enabling more strategic development of the field. MSI’s Buried Arrays are specially designed for each project to maximize coverage and typically cover anywhere from 15 to more than 150 Square miles (24 to 242 square km) depending on the well locations and required spacing. The Buried Array, along with MicroSeismic’s patented PSET^® processing technology, has gained industry acceptance and has proven to provide more accurate and comprehensive results when compared to down hole monitoring methods. In addition, the Buried Array, like the FracStar^® array from MicroSeismic, does not require a monitor well, which is required with down-hole monitoring methods.

The Buried Array system is designed to be permanently placed into the ground for monitoring, whenever it is required. Specially designed geophones are buried several hundred feet below the surface of the earth to avoid the surface noise that is problematic when recording seismic data. In addition to the monitoring of hydraulic fracturing operations, the Buried Array is also used for Life of Field (LOF) studies, "Heavy oil production"/Steam Assisted Gravity Drainage (SAGD), CO2 sequestration monitoring, and the monitoring of geothermal projects, reservoir subsidence, and steam and water injection programs.

MicroSeismic, Inc. has Buried Arrays installed in the Haynesville, Bakken and Marcellus shale plays and is currently planning to implement Buried Arrays in the other emerging shale plays in the US and Canada.

Increasing Production While Lowering Costs

Surface data acquisition is cost effective using large channel count arrays for short-term jobs over several days or weeks. However, for long term hydraulic fracturing and reservoir monitoring projects covering multiple wells, a permanently buried array using fewer geophones is a more cost effective acquisition method. It provides extremely high resolution, accurate results, and it is the best commercial and technical option for long-term field monitoring.

Burying a limited number of geophones 300 feet (92m) deep reduces the surface noise and increases the signal to noise (S/N) ratio allowing for a reduction in channel count and simplifying the acquisition system and services.

Greater Coverage with a Buried Array

Overview:

• Array of 80 – 100 geophones buried to 300’
• Coverage 25 to 150+ square miles per installation
• Pre-installation localized testing
• Array layout designed for specific target and local conditions
• Custom 3-C phones and installation
• Innovative acquisition equipment
• PSET^® processing from MicroSeismic
• Advanced interpretation solutions provides additional critical information to client

Deploying a Buried Array

Prior to designing the array for any given area, a noise survey is done. This allows for optimization of key parameters such as depth of burial, sensor density and, grid biasing.

Geophones are permanently installed at a depth of approximately 300 feet (100 meters) and use MicroSeismic’s proprietary processing technology known as PSET^®, or Passive Seismic Emission Tomography to map the location of microseismic activity in the development area, within the target volume over an extended period of time (from months to years).

The buried array utilizes “beam forming” or stacks the output from the entire array of geophones, allowing for identification and location of micro seismic events that are below the ambient noise level on individual receiver traces.

Deployment of a buried array requires the burial of approximately 100, 3-Component geophones to monitor microseismic activity at reservoir depth within an approximate development area. Monitoring microseismicity over a large reservoir volume provides for detailed mapping of the production and/or injection volume. This detailed mapping allows for the optimization of several key development and completion parameters for multiple wells within the monitoring area.

For unconventional development projects such as gas shale and tight sand reservoirs, this array provides a cost-effective, long-term method for optimizing the following:

• Development well azimuth relative to local and regional stresses
• Infill well spacing and lateral length
• Hydraulic fracture geometry and containment
• Individual well stimulation
• Long term production monitoring for geo-mechanical and drainage area analysis

Benefits of the Buried Array:

• Commercially viable monitoring of all wells in a large development area
• High resolution results over 25+ square miles
• Allows rapid optimization of completions strategy
• Provides statistically valid sampling
• Allows long term production monitoring
• No depth, temperature, or location limitations on monitoring
• Large aperture array allows for advanced attribute analysis
• The recording system is easily deployed shortly before each fracture monitoring job, and picked up immediately afterwards. This allows the data acquisition efforts to adapt easily to the field development hydraulic fracturing program.
• Long term monitoring of production related microseismic activity can be economically achieved over large reservoir volumes.
• The acquisition array is independent of any wellbores, eliminating the need to enter a wellbore for each monitoring program.
• Each autonomous digitizer/recording systems are GPS timed providing globally synchronous recording with any auxiliary instrument.
• Burial of the geophones below the wave-guide formed by the near-surface allows for stacking of higher frequencies (improves X, Y, & Z resolution)
• The Buried Array is significantly less expensive to install and maintain than a permanently installed downhole array or repeated mob/install/pickup/de-mob of temporary surface or downhole arrays.
• The Buried Array system array can be quickly and inexpensively expanded if additional reservoir volume needs to be monitored.

This image shows typical results from a Haynesville well monitored using a buried array. Induced fracture growth is predominantly in the direction of maximum horizontal stress. Stage spacing appears to be optimized in this well with little overlap or gaps between stages.

ADDITONAL USES OF A BURIED ARRAY FOR MICROSEISMIC MONITORING:

• Geothermal mapping
• Mine integrity
• Seal integrity for gas storage
• Hydraulic fracture stimulation
• Primary/secondary/tertiary recovery

MicroSeismic, Inc. Buried Arrays in the Haynesville Shale are helping operators increase production and reduce their costs by enabling them to improve the overall efficiency and effectiveness of their frac programs.