SWDI Investors’ Guide – SWDs and Earthquakes, Part 2                            April 15, 2013

Introduction
Induced earthquakes have been mentioned several times in this blog. In the past few weeks, however, a new technical paper has been published and has received widespread coverage in the media. The paper contains considerable new data and new interpretation that bears upon the interconnection of deep disposal wells and shallow earthquakes. We will attempt to summarize the paper and assess how the research changes our views of SWD and earthquakes and whether this new paper could have implications for regulatory control of deep injection wells.

Keranen, K.M., H.M. Savage, G.A. Abers, and E.S. Cochran et al: Potentially induced earthquakes in Oklahoma: Links between wastewater injection and the 2011 M_w 5.7 earthquake sequence. Geology, published online 26 March 2013.  (http://geology.gsapubs.org/content/early/2013/03/26/G34045.1.abstract)
This is the paper prepared by scientists from University of Oklahoma, Columbia University, and the US Geological Survey. Historically the quake sequence contained the largest events in the history of the state and caused significant damage in south Lincoln County in central Oklahoma. Lincoln County is home to a large oil and gas infrastructure including three commercial disposal wells and 657 total disposal and injection wells. Old oil wells are still in operation producing oil and saltwater at the same time new plays are being developed in the county.

The article carried new seismological data surrounding the November 2011 quakes near Oklahoma City. New data allowed more precise geographical and depth location of the big quakes and the aftershocks. In addition modern 3-D seismic data was used to locate large faults and associated smaller faults in the area of Prague, Oklahoma. Earthquake data and 3-D seismic were used together in the paper, which included the map shown here as Figure 1. The map locates the two large earthquakes plus the many other after-shocks within the approximately four-mile by six-mile area. The two deep injection wells shown in red triangles are situated in Sec 35 – 13N – 5E; these are the Spess Oil Stasta-2 in the NW-NW of Sec 15 and the New Dominion Wilzetta 1-SWD in the SW-NE of Sec 15. Both of these wells inject into the Arbuckle carbonates and Wilcox sands. The wells are shown in the new paper on a cross-section paralleling the fault trends; this cross-section is plotted on Figure 1and is reproduced as Figure 2 below.

 

Figure 1:  Oil wells, injection wells, faults, and earthquakes in SE Lincoln County
(Cross-Section in Red in Figure 2)
Source: Keranen et al, 2013

Figure 2: Cross-Section across map with disposal wells and quakes. Colors of dots represent time-slices. Yellow band is the approximate limits of the Arbuckle Formation. Green band is Hunton plus Wilcox Formations.
Source: Keranen et al, 2013

Figure 3. Injection rate and injection pressure compared to earthquake rate from the beginning of 2010 through the end of 2011. No short-term correlation between injection parameters and seismicity is evident in these data. For consistency, earthquakes throughout the two years are those reported in the Oklahoma Geological Survey catalog, of M1.5+, occurring within the region of Figure 1.

Figure 3 data include consistent quake counts taken only from the OGS array and injection statistics reported by the operators. The rates of injection vary from approximately 4,000 to 6,000 bbls per month in the time period of the seismic events; this averages out to approximately 100 to 200 bbls per day. We don’t believe that these reports are accurate nor do they represent even an approximation of the injection activity. The Spess Oil well may be averaging 100 bbls per day but the New Dominion well should be averaging 100 times that amount in order to service the operator’s waste water needs. New Dominion is a leader in the industry sector of “de-watering” old oilfields by producing water at very high rates with large, submersible pumps. This activity calls for high-capacity disposal wells operating at maximum rates.

Regulatory Implications
Previous blogs have addressed the environmental risks represented by deep disposal wells, especially associated with induced earthquakes. Many studies have described relationships but the most applicable example of injection and earthquakes was not studied in detail until now. This paper describes the possible cause of the Prague earthquakes as being the injection wells in very close proximity – both geographically and depth-wise. What is missing from the present study is a credible smoking gun. We think that the New Dominion well could be that powerful factor missing from the paper. If a credible injection rate could be found, we think it would put the Prague, Oklahoma quakes into the dimensions of the other induced quakes. 

A later blog post will explore the full regulatory implications of the many studies that have linked deep injection wells to induced earthquakes.

Investors considering a SWD project must investigate the pros and cons of the specific project whether it is in operation or is meant to be drilled and the surface facilities built from scratch. An experienced, full-service contractor such as SWDI can help evaluate the project.

Bruce G. Langhus, PhD                                                                            Marian M. Smith, PhD