Deploying Wireless Seismic Recording Systems for Real-time

Monitoring and Analysis of Hydraulic Fracturing Projects

D.B. Crice & M. Lambert* (Wireless Seismic Inc.)R. Evans & P. Morton (MicroSeismic Inc.)

• There are markedly different logistical requirements for Hydraulic Fracture Monitoring projects than for traditional active reflection seismic projects.• Projects need to be coordinated with frac job. • Ease of deployment and retrieval of the system is paramount to ensure

efficient and flexible operations. • Results often need to be delivered as soon as possible during or after

each frac. • Logistics of a wired system can be challenging with surface access

restrictions, natural topography and structures such as rivers, highways, and fences.

The need for real-time microseismic

• Since real-time processing and analysis of the recorded passive seismic data is often a HFM requirement, the acquisition system has to be able to deliver continuous and uninterrupted data from each station.• Data can be processed in real-time allowing on-site frac engineers to

view the results at the time of the frac. This provides them with actionable information with which they can diagnose and quantify the efficacy of each stage.• In this poster, we introduce a large-scale wireless and cable-less

seismic recording system for rapid and cost-effective deployment with real-time data streaming for in-field processing and analysis. The advantages of the wireless and cable-less system and the benefit to clients from the availability of real-time results will be discussed.

The need for real-time microseismic

• Accurate, usable microseismic data recorded during hydraulic fracture treatments is critical for successful monitoring of the frac, yielding results that include an understanding of the fracture height, half-length, and azimuth.

• Given the immediacy of the operation, there is no opportunity to reacquire data.

• The data acquisition system employed for surface microseismic has to be reliable, field deployable under a variety of conditions, and capable of delivering streaming data continuously during the frac operation.

• The system must also perform diagnostic checks during the deployment and the frac job, as well as adjust for any problems.

• Field test of wireless seismic equipment, set side-by-side with a cabled system.

• Background noise was measured for each system for 24-hours and plotted.

• Resultant plots from the wireless and cabled systems showed comparable noise response.

• The wireless system proved to be less susceptible to section drop-outs due to severed cables (caused by wildlife, livestock, vehicles, equipment, etc.).

Screen capture showing the status of each acquisition channel, microseismic events, and a real-time noise monitor for the array.

How can thousands of radios to talk to the central recorder simultaneously? At low power?

• Make each radio a relay.– Units only need to communicate by one group

interval.– Data is passed from unit to unit until it reaches

the backbone.– The backbone carries the data to the central by

high-speed link or fiber optic.

The lack of cables means:• During layout, the capability to

skip over surface hazards and obstacles is extremely advantageous. • Surface obstructions such as

rivers, lakes, roads, railroad tracks, etc. can severely hinder optimal array design and data acquisition. • Permit restrictions can be

mitigated or avoided altogether by “jumping over” these obstructions.• In this figure, several impassable

areas (yellow boxes) associated with a river did not affect the shape and arrangement of the arms of the array.

Individual traces of monitoring data are sent from each array station to the recorder, quality checked, and saved on a Network Attached Storage (NAS) device. From the NAS, seismic data are continually transferred to the Graphics Processing Unit (GPU). Preliminary trace processing is performed before the application of the imaging algorithm.

Results delivered to the user in near real time

• Visualization images can be broadcast live on the internet to any interested parties through web based video conferencing applications. • The images can also be relayed back to the recording truck, frac van, or

even to smart phones, tablets, or PDAs. The entire process generally takes 5 to 10 minutes after the event occurrence.• Central to the ability to image microseismic activity in real-time is the

imaging algorithm, (Thornton, M.P, Eisner, L., 2003) using a travel-time table constructed from an appropriately calibrated velocity model. • This velocity model can also compensate for anisotropy observed in

the local geology (Eisner, et al., 2011). The technique employs beam steering to gather and sum the seismic data input and can detect microseismic event hypocenters with high accuracy.

Regulatory Trends Toward Real-Time Monitoring

• UK exploration resumes with new controls to mitigate risk– Seismic monitoring must be carried out before, during, and after

hydraulic fracturing.– A new traffic light system to categorize seismic activity.– Trigger mechanism will stop hydraulic fracturing operations in certain

conditions.• DNV launches global recommended practice for shale gas risk

management– Draft standard for shale gas development and operations.– Includes requirement for real-time microseismic monitoring before,

during, and after hydraulic fracturing.

Frac Monitoring Project Example• Shown here are partial results

from a project in a multi-well field (Kratz, et al., 2012).• The HFM data were collected

with a surface array without real-time processing.• Analysis of this section of the

well reveals a linear trend of microseismic events (shown in blue) far from the treatment well. • Results indicate that

treatment fluids leaked into a natural fault in the reservoir. • Real-time monitoring could have revealed the far afield events during

pumping; allowing the operator the option to change the pumping plan.

Real-time monitoring offers the opportunity to change fracturing operations as a result of the

reservoir’s response to treatment

• Determining overall frac effectiveness: – Real-time monitoring can determine the effectiveness of treatments

on individual stages and show that stimulation has achieved design targets saving resources.

• Changing fracture treatment parameters: – Fracture treatment parameters can be changed from stage-to-stage.

Corresponding changes in the microseismic response can be used to identify optimum stage spacing and perforation gun arrays as well as determine optimum fluid volumes, rates and proppant.

– Real-time provides preliminary microseismic results while the field crews are still on site enabling on-demand program changes. This can reduce overall project cycle time significantly.

Real-time monitoring offers the opportunity to change fracturing operations as a result of the

reservoir’s response to treatment

• Ensuring activity stays within zone: – In the Fort Worth Basin in the southern USA, real-time monitoring can

be used to detect activity breaking out of the Barnett Shale into the underlying, water charged, Viola or Ellenberger carbonates.

• Identifying Geohazards: – Sub-seismic faults can be reactivated during frac operations. If fault

reactivation occurs, the stimulation may be directed away from the reservoir objective resulting in little production.

• Mapping Induced seismicity: – Real-time monitoring can be used to detect microseismic build-up to

larger seismic events. Identification of precursor seismicity can allow an operator to change fracturing parameters (e.g., pressures, flow rates) or to terminate a stage entirely to avoid initiating larger events.

References

• Eisner, L., Zhang, Y., Duncan, P., Mueller, M.C., Thornton, M.P., & Gei, D, 2011, Effective VTI anisotropy for consistent monitoring of microseismic events: The Leading Edge, 30, no.7, 772-776.

• Kratz, M., Hill, A., &Wessels, S. (2012). Identifying Fault Activation in Unconventional Reservoirs in Real Time Using Microseismic Monitoring. SPE Unconventional Resources Conference, Extended Abstracts, SPE 153042.

• Thornton, M.P, Eisner, L. (2003). U.S. Patent No. 7,978,563. Washington, DC: U.S. Patent and Trademark Office.

• UK Controls www.shale-gas-information-platform.org/areas/news/detail/article/uk-exploration-resumes-with-new-controls-to-mitigate-seismic-risks.html

• DNV Standard www.dnv.com/press_area/press_releases/2013/dnv_launches_global_recommended_practice_for_shale_gas_risk_management.asp?goback=%2Egmr_2241563%2Egde_2241563_member_210549656