07123-06

Goal
This project seeks to determine if seismic stimulation can increase oil production in mature oil fields where production is declining. The research team will perform field tests of seismic stimulation at an oil reservoir in Oklahoma, as well as test the physical basis for how this stimulation process might work.

Performers
Lawrence Berkeley National Laboratory, Berkeley, CA 94729
Berkeley GeoImaging Resources, LLC, Oakland, CA 94606

Background
Evidence that seismic waves directed into a reservoir can enhance oil production can be found in the literature beginning in the 1950s. The Department of Energy (DOE) has sponsored three projects related to seismic stimulation over the past 10 years. The first was a jointly led effort by Los Alamos National Laboratory (LANL) and Lawrence Berkeley National Laboratory (LBNL) and focused on making successful laboratory measurements of vibrationally enhanced oil production, quantifying the amplitude of stimulation sources used in the field, and quantifying the changes in production in a very low-permeability diatomite reservoir (Lost Hills) near Bakersfield, CA. At Lost Hills, oil production increased by 24% during the 2 months of stimulation.

The second project, led by Oil & Gas Consultants International, aimed to quantify the changes in production from a sandstone reservoir in Oklahoma using a “whirling mass” downhole stimulation source. Unfortunately, the source became stuck in the well and ceased operation before any effect could be quantified.

The third project was led by Michigan Technical University and aimed to quantify the seismic amplitudes coming from four different seismic sources to determine which was best for stimulation. This project also had a theoretical aspect in that it attempted to explain the physical basis of seismic stimulation. The idea that seismic waves can push oil ganglion or “bubble” through pore throats, overcoming the capillary forces that are blocking them from moving, is what the present quantitative theory is based upon.

The most definitive field tests to date of seismic stimulation have been conducted by Occidental Petroleum Corp. in a sandstone reservoir at Elk Hills, CA. Oxy has been using the Hydro-Impact seismic source made by Applied Seismic Research (ASR), which represents the state-of-the-art in large amplitude downhole sources. It works by compressing well water in a chamber at the base of the pumping rod string. The compressed water is suddenly released downward causing seismic waves to be created. Each plunger cycle takes 7 to 10 seconds and the source is designed to run continuously for up to 6 months.

This project will involve a field trial of seismic stimulation at an oil reservoir in Osage County, Oklahoma operated by Berkeley GeoImaging Resources, LLC, where production from individual wells will be monitored for 8 months prior to stimulation and for at least 8 months after stimulation begins. Using 3D seismic data, modern well logs, cores, and production data, a comprehensive 3D reservoir model will be constructed that allows numerical predictions to be made of where the stimulation is expected to liberate trapped oil. Comparisons between the numerical predictions and individual well production histories will be used to draw conclusions about seismic stimulation. This research will provide the most complete test of seismic stimulation to date.

Deliverables for this project will include a series of reports on the tasks as they are completed and a final report integrating the results of the project.

Potential Impacts
A comprehensive scientific assessment of the potential for seismic stimulation could provide evidence to justify the development and application of an entirely new methodology for increasing oil production in mature oil fields. Seismic stimulation is less expensive than CO2 and thermal EOR methods. Seismic stimulation may also reduce water cuts in stripper wells and extend the production life of these wells.

Accomplishments
The Project Management Plan and the Technology Status Assessment have been completed.

The seismic source to be used for the stimulation has been built and several new production wells have been drilled in the field.

A problem has been well-by-well monitoring of production in the field to establish the baseline prior to stimulation. After performing quality control on the production data collected by BGI, LBNL determined, in November, 2009, that the existing data was not sufficient and a new production monitoring protocol was required. So BGI and LBNL agreed to have two new mobile monitoring rigs built. These trailer mounted rigs hook up to a well head and monitor gas, oil and water cuts, in addition to total flow, for a 24 hour period. The new system monitors two wells each day. All of the wells of interest are monitored once every 2 to 3 weeks. Pre-stimulation monitoring began in mid 2010.

LBNL has built a first reservoir and seismic model for the field in Osage Co., OK and developed the ability to combine hydrological and seismic modeling to make maps of where seismic stimulation is expected to have its greatest effect. Because the reservoir model has been built without production data, the permeabilities must presently be estimated (the downhole pressure and average flow rates in the entire field are used to estimate permeability but this will improve once the new monitoring system is deployed and operational).

Current Status (January 2010)
The project is roughly one year behind schedule because of the inability to properly monitor the field on a well-by-well basis. A detailed plan is now in place for the remainder of the project including which well to use for the seismic source and which part of the field to focus on for the stimulation test. The current expected calendar for the project is as follows:

May through August, 2010 - monitor the production in the field on a per-well basis for the four months prior to stimulation. Use the new production data to update the reservoir model. Make maps of the so-called “seismic stimulation potential.”

September, 2010 through April, 2011 - run the seismic source and monitor the well-by-well production response of the field. We will be installing several strings of down-hole geophones in the field that will be used to monitor (record) the strength of the seismic source on a continuous basis over the expected 8 month lifespan of the source. Update the stimulation potential map with the recorded values of the seismic amplitudes in the field. Compare these theoretical predictions to production results as they come in.

June, 2011 through September, 2011 - monitor production for four months in the field once the seismic source has been turned off. Write up and disseminate all results.

This project will not have any cost overruns and will come in one year late from the original end date. As a result a request for an extension until September 30, 2011 will be submitted.

Project Start: October 1, 2008
Project End: February 28, 2011

DOE Contribution: $723,373
Performer Contribution: $650,000

Contact Information:
RPSEA – Martha Cather (martha@prrc.nmt.edu or 575-835-5685)
NETL – Chandra Nautiyal (Chandra.Nautiyal@netl.doe.gov or 281-494-2488)
Performer Company – Steven R. Pride (srpride@lbl.gov or 510-495-2823)