Disposal Wells Research Articles

Microseismicity Induced by Deep Wastewater Injection in Southern Trumbull County, Ohio

Online Material: Description and figure representing the stratigraphy and construction of the two wastewater disposal wells. As oil and gas well completions utilizing multistage hydraulic fracturing have become more commonplace, the potential for seismicity induced by the deep disposal of frac‐related wastewater and the hydraulic fracturing process itself has become an increasingly important issue (e.g., National Academy of Science [NAS], 2012). Although it is rare for a wastewater disposal well to induce felt seismicity, there have been several cases over the past half century that identify strong relationships between injected fluids and seismicity (e.g., Healy et al. , 1968; Nicholson and Wesson, 1990; McGarr et al. , 2002; Evans et al. , 2012). Following the 2011 Youngstown earthquake sequence (YES) near a wastewater disposal well in northeastern Ohio (Fig. 1), which included hundreds of earthquakes up to an M 4.0 (Ohio Department of Natural Resources [ODNR], 2012; Kim, 2013; Skoumal, Brudzinski, Currie, et al. , 2014), there has been a heightened concern over seismicity related to energy technologies in Ohio. The ODNR is actively setting new regulations to deal with induced seismicity (ODNR, 2014), which could serve as a blueprint for other states. Seismic monitors are to be installed near certain injection wells before commercial injection begins and will remain there for 12 months afterward. A number of regional long‐standing backbone seismic stations have been operating for over a decade, and studies of the YES significantly benefited from early adoption of EarthScope Transportable Array (TA) stations in western Pennsylvania in late 2010. Figure 1. Location of the study region (box in the lower inset), with enlarged views showing seismic stations (black triangles) and cases of seismicity that are potentially induced by injection wells (gray) or hydraulic fracturing (white). The white box in the central map is the location of the upper …

Data inconsistencies from states with unconventional oil and gas activity

The quality and availability of unconventional oil and gas (O&G) data in the United States have never been compared methodically state-to-state. By conducting such an assessment, this study seeks to better understand private and publicly sourced data variability and to identify data availability gaps. We developed an exploratory data-grading tool - Data Accessibility and Usability Index (DAUI) - to guide the review of O&G data quality. Between July and October 2013, we requested, collected, and assessed 5 categories of unconventional O&G data (wells drilled, violations, production, waste, and Class II disposal wells) from 10 states with active drilling activity. We based our assessment on eight data quality parameters (accessibility, usability, point location, completeness, metadata, agency responsiveness, accuracy, and cost). Using the DAUI, two authors graded the 10 states and then averaged their scores. The average score received across all states, data categories, and parameters was 67.1 out of 100, largely insufficient for proper data transparency. By state, Pennsylvania received the highest average ( = 93.5) and ranked first in all but one data category. The lowest scoring state was Texas ( = 44) largely due to its policy of charging for certain data. This article discusses the various reasons for scores received, as well as methodological limitations of the assessment metrics. We argue that the significant variability of unconventional O&G data—and its availability to the public—is a barrier to regulatory and industry transparency. The lack of transparency also impacts public education and broader participation in industry governance. This study supports the need to develop a set of data best management practices (BMPs) for state regulatory agencies and the O&G industry, and suggests potential BMPs for this purpose.

Geochemical and isotopic evolution of water produced from Middle Devonian Marcellus shale gas wells, Appalachian basin, Pennsylvania

The number of Marcellus Shale gas wells drilled in the Appalachian basin has increased rapidly over the past decade, leading to increased interest in the highly saline water produced with the natural gas which must be recycled, treated, or injected into deep disposal wells. New geochemical and isotopic analyses of produced water for 3 time-series and 13 grab samples from Marcellus Shale gas wells in southwest and north central Pennsylvania (PA) are used to address the origin of the water and solutes produced over the long term (>12 months). The question of whether the produced water originated within the Marcellus Shale, or whether it may have been drawn from adjacent reservoirs via fractures is addressed using measurements of and activity. These parameters indicate that the water originated in the Marcellus Shale, and can be more broadly used to trace water of Marcellus Shale origin. During the first 1–2 weeks of production, rapid increases in salinity and positive shifts in values were observed in the produced water, followed by more gradual changes until a compositional plateau was reached within approximately 1 yr. The values and relationships between Na, Cl, and Br provide evidence that the water produced after compositional stabilization is natural formation water, the salinity for which originated primarily from evaporatively concentrated paleoseawater. The rapid transition from injected water to chemically and isotopically distinct water while of the injected water volume had been recovered, supports the hypothesis that significant volumes of injected water were removed from circulation by imbibition.

Mechanism of Intraplate Earthquakes and Anthropogenic Causes in USA

In this paper we carried out an investigation about the possible causes for the enhancement of earthquakes in USA the last seven years. Our statistical and physical models indicated that the increased evolution of events in the country depends from the human actions. For further analysis we divided the country into three main seismological regions: western, central and, eastern. We roughly classified the areas by their thickness of Earth’s crust in a variation 25-45-25 km. The thickest area is in the mid-continent and most of this region are part of the Great Plains. In our study we are going to investigate the reason for the Mississippi Lime in Oklahoma a very thick area, started an unusual earthquake activity since 2010, most at Oklahoma/Kansas border. In this region also there are many anthropogenic activities concerning with the waste water wells and more than 4000 of them are active in the state. Wastewater disposal wells typically operate for longer duration and inject much more fluid than hydraulic fracturing, making them more likely to induce earthquakes. Enhanced oil recovery injects fluid into rock layers where oil and gas have already been extracted, while wastewater injection often occurs in never-before-touched rocks. Therefore, wastewater injection can raise pressure levels more than enhanced oil recovery, and thus increases the likelihood of induced earthquakes. Most injection wells do not trigger felt earthquakes. A combination of many factors is necessary for injection to induce felt earthquakes. These include the injection rate and total volume injected; the presence of faults or unknown fractures that are large enough to produce felt earthquakes; stresses that are large enough to produce earthquakes; and the presence of pathways for the fluid pressure to travel from the injection point to faults. Finally other causes of human action triggering earthquakes fluid injection, hydraulic fracturing, enhanced oil recovery, mining, nuclear explosions, some of them will be mentioned and investigated in this paper. We also intend to explain why not all the waste wells are triggering earthquakes and how it would be strongly attached to the unevenness of the Earth’s crust.

에너지개발기술에 있어 유체주입에 따른 유발지진 발생 사례분석

Induced seismicity related to four energy development technologies that involve fluid injection or withdrawal: geothermal energy, conventional oil and gas development including enhanced oil recovery (EOR), shale gas recovery, and carbon capture and storage (CCS) is reviewed by literature investigation. The largest induced seismic events reported in the technical literature are associated with projects that did not balance the large volume of fluids injected into, or extracted from the underground reservoir. A statistical observation shows that the net volume of fluid injected and/or extracted may serve as a proxy for changes in subsurface stress conditions and pore pressure, and other factors. Energy technology projects that are designed to maintain a balance between the amount of fluid being injected and the amount of fluid being withdrawn, such as geothermal and most oil and gas development, may produce fewer induced seismic events than technologies that do not maintain fluid balance, such as long-term wastewater disposal wells and CCS projects.

Technology Focus: Water Management (December 2014)

Technology Focus The demands for fresh water used in hydraulic-fracturing operations are placing constraints on water resources in some regions of the United States. Because of the high volumes of fresh water needed for hydraulic fracturing, the competing demand driven by industrial, municipal, and agricultural users has decreased the availability of fresh water and increased associated costs. Along with higher acquisition costs for fresh water, produced-water-disposal costs also have increased. To overcome these challenges, operators are using alternative methods of water management, including recycling and reusing produced water, to help reduce the total amount of fresh water required for their fracturing operations and, at the same time, reduce the amount of produced water that must be transported, treated, and disposed of. If the produced water is not recycled, the water is pumped into disposal wells. This practice has become a topic of public concern after reports of earthquakes began approximately 4 years ago in the central United States, where disposal wells are heavily used. Research conducted by the US Geological Survey and universities suggests that the increased injection of produced water from oil and gas operations near fault zones may be inducing earthquakes. Reclaiming produced water as a base fluid for hydraulic fracturing not only helps alleviate the oil and gas industry’s dependence on fresh water but also lowers the overall cost of fracturing. Produced water is usually composed of formation water and injected fluids from previous fracturing treatments. It can contain hydrocarbon and high levels of total dissolved solids (TDS), along with suspended solids and residual production chemicals. To reuse high-TDS produced water effectively in crosslinked-gel- based hydraulic-fracturing fluids, the water must first be treated. The goal of treatment is to control ions that hinder the development of the stable crosslinked fluid or that cause scale buildup in the wellbore. In response, a growing group of chemical suppliers, researchers, and service companies is on a mission to develop chemicals that will enable guar to hydrate and crosslink with boron crosslinker in untreated, high- TDS produced waters and yield a stable crosslinked fracturing fluid. The papers featured this month deal with water management and produced-water- treatment technologies. I urge you to look at OnePetro, the SPE online library, and download papers. You will find updates on best practices, case studies, new treatment technologies, and much more. JPT Recommended additional reading at OnePetro: www.onepetro.org. SPE 168520 One Company’s Upstream- Water-Resources-Management Guide by Stuart R.D. Lunn, Imperial Oil, et al. SPE 168401 Chevron San Ardo Facility Unit Beneficial Produced-Water Reuse for Irrigation by James E. Myers, Chevron SPE 168568 Appalachia Shale-Gas- Water Management Best Practices by Sean Beecroft, Chevron, et al. SPE 168469 Water Worth Waiting for: Smart Water Management Reduces Environmental Impact by S. Monroe, Baker Hughes, et al. SPE 165138 Produced-Water- Reinjection Design and Uncertainties Assessment by Jalel Ochi, Total, et al.

Advanced Technologies for Produced-Water Treatment and Reuse

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 17394, ’Advanced Technologies for Produced-Water Treatment and Reuse,’ by A. Hussain, J. Minier-Matar, A. Janson, S. Gharfeh, and S. Adham, ConocoPhillips, prepared for the 2014 International Petroleum Technology Conference, Doha, Qatar, 20-22 January. The paper has not been peer reviewed. Historically, the treatment of produced water (PW) has been limited to free-oil and suspended-solids removal, using physical separation technologies and injection in disposal wells. However, because of new regulations, combined with geological restrictions and local water scarcity, the drive to have a greater fraction of the PW treated more extensively and ultimately to be reused is increasing. This paper presents the results of a laboratory investigation in which treatment processes were evaluated as treatment methods for PW from different oil and gas fields. Introduction A combination of factors is putting great pressure on operators to find new ways of treating and managing PW that promote water conservation and sustainability. However, treating PW to produce a good-quality effluent is a challenging task. PW characteristics can vary considerably. In order to treat PW to a water-quality standard that enables it to be reused, advanced water-treatment technologies (AWTTs) have to be applied, alone or in combination. To investigate the suitability of several AWTTs to treat and reuse PW from Qatari gas fields, the authors, in conjunction with an operator’s research center, carried out a laboratory investigation in which various treatment processes were evaluated. Four treatment methods were selected to target main contaminants identified in PW from a Qatari gas field: Membrane processes were used to target field chemicals, membrane-distillation (MD) methods were used to target salinity, membrane-bioreactors (MBRs) were used to target organics, and ozonation was used to target field chemicals. Overview of AWTTs Membrane Processes. The potential for membrane processes to treat PW has been demonstrated successfully in various field studies; moreover, a number of upstream petroleum full-scale facilities have already installed membrane processes to treat and reuse PW. The treatment trains either are a combination of different membrane processes or involve other conventional water-treatment technologies such as media filtration or clarification. For two case studies involving the use of membrane processes, please see the complete paper. Thermal Evaporators. These entered the PW-treatment market by finding niche opportunities. Moreover, because almost all waste streams are recycled back to the evaporator, the volumes of fresh water required for makeup are dramatically reduced. With the proliferation of shale-gas wells in the past decade in the US, the demand for treating flowback water with total-dissolved-solids (TDS) concentrations greater than 100 000 mg/L has expanded the opportunities for thermal systems. Another niche market in which the application of evaporators has been very successful is the steam-assisted- gravity-drainage enhanced-recovery process. MBRs. MBRs are now considered by the downstream petroleum industry as an excellent solution to treat various wastewater streams. Although MBRs have not yet been applied to treat PW at upstream oil and gas facilities, a number of bench-scale and pilot studies report that PW is biodegradable, achieving chemical-oxygen-demand (COD) and oil-and-grease (O&G) removals greater than 95%. Moreover, full-scale MBRs are also operating successfully in other industries, treating highly contaminated organic streams (COD greater than 15 000 mg/L) and achieving COD removals greater than 95%.

Assessment of the likelihood of suffusion in alluvial soils: case history

Suffusion is a process of soil particle transfer in the soil body due to the effect of seepage flow on it. Although up to now internal instability has been considered in hydraulic structures such as dikes, dams and canals, todays, occurring of this phenomenon in arid regions and non-hydraulic constructions was seen. Shahriyar County in Iran, located on alluvial soil deposits, is an area where the non-hydraulic structures built there have been damaged by erosion. Even though there is no surface water flow, a seepage force has been generated by water leakage from buried pipes and sewage disposal wells. In this article, we tried to determine whether suffusion occurs in Shahriyar. Because of the limited number of available methods for the assessment of suffusion, in this article, a new approach is presented using statistical analysis to assess the internal instability of alluvial soils. This approach was developed and verified using a relatively large database of unstable soils. The performance of the presented approach was compared with those of three commonly used methods. It is showed this approach can predict the likelihood of internal instability with a relatively high accuracy rate.

The 2001-Present Induced Earthquake Sequence in the Raton Basin of Northern New Mexico and Southern Colorado

We investigate the ongoing seismicity in the Raton Basin and find that the deep injection of wastewater from the coal-bed methane field is responsible for inducing the majority of the seismicity since 2001. Many lines of evidence indicate that this earthquake sequence was induced by wastewater injection. First, there was a marked increase in seismicity shortly after major fluid injection began in the Raton Basin in 1999. From 1972 through July 2001, there was one M ≥ 4 earthquake in the Raton Basin, whereas 12 occurred between August 2001 and 2013. The statistical likelihood that such a rate change would occur if earthquakes behaved randomly in time is 3.0%. Moreover, this rate change is limited to the area of industrial activity. Earthquake rates remain low in the surrounding area. Second, the vast majority of the seismicity is within 5 km of active disposal wells and is shallow, ranging between 2 and 8 km depth. The two most carefully studied earthquake sequences in 2001 and 2011 have earthquakes within 2 km of high-volume, high-injection-rate wells. Third, injection wells in the area are commonly very high volume and high rate. Two wells adjacent to the August 2011 M 5.3 earthquake injected about 4.9 million cubic meters of wastewater before the earthquake, more than seven times the amount injected at the Rocky Mountain Arsenal well that caused damaging earthquakes near Denver, Colo- rado, in the 1960s. The August 2011 M 5.3 event is the second-largest earthquake to date for which there is clear evidence that the earthquake sequence was induced by fluid injection.

Searching for Solutions to Induced Seismicity

Induced Seismicity A sharp rise in seismic events in some areas of the United States where oil and gas production is booming is leading regulators and the industry to examine whether the two are related. And beyond that—what can be done to address the situation. In the first 6 months of this year in Oklahoma, for example, 268 earthquakes measuring higher than magnitude 3.0 have taken place in a state that experienced no more than three earthquakes a year of that magnitude from 1991 to 2008. The data comes from both the Oklahoma Geological Survey (OGS) and the United States Geologic Survey (USGS), the respective state and federal agencies tasked with studying the natural sciences, including earthquake hazards. Mark Zoback, a Stanford University geophysics professor and a director of the Stanford Center for Induced and Triggered Seismicity (SCITS), said that although it has been known since the 1960s that fluid injection is capable of triggering earthquakes, the ongoing sequence of small to moderate magnitude seismic events so far inside the interior of a continental tectonic plate is unprecedented. One of the leading fault mechanics experts in the world, Zoback’s research is heavily cited by both government and industry studies on induced seismicity. “This kind of increase in seismicity has not been seen in the modern era, so it is a very unusual phenomenon,” said Zoback, who wrote or cowrote nearly 300 technical papers. “Many of these are earthquakes that are above magnitude 3.0, which means that they are being widely felt.” In January, the USGS issued a report titled “Man-Made Earthquakes Update.” It said the rise in seismicity in the central and eastern US that started around 2009 has coincided with the injection of waste water from oil and gas operations into deep disposal wells in several states, including Colorado, Texas, Arkansas, Oklahoma, and Ohio.

Wastewater disposal linked to earthquakes

Induced Earthquakes The number of earthquakes is increasing in regions with active unconventional oil and gas wells, where water pumped at high pressure breaks open rock containing natural gas, leaving behind wastewater in need of disposing. Keranen et al. show that the steep rise in earthquakes in Oklahoma, USA, is likely caused by fluid migration from wastewater disposal wells. Twenty percent of the earthquakes in the central United States could be attributed to just four of the wells. Injected fluids in high-volume wells triggered earthquakes over 30 km away. Science , this issue p. [448][1] [1]: /lookup/volpage/345/448?iss=6195

Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection

Unconventional oil and gas production provides a rapidly growing energy source; however, high-production states in the United States, such as Oklahoma, face sharply rising numbers of earthquakes. Subsurface pressure data required to unequivocally link earthquakes to wastewater injection are rarely accessible. Here we use seismicity and hydrogeological models to show that fluid migration from high-rate disposal wells in Oklahoma is potentially responsible for the largest swarm. Earthquake hypocenters occur within disposal formations and upper basement, between 2- and 5-kilometer depth. The modeled fluid pressure perturbation propagates throughout the same depth range and tracks earthquakes to distances of 35 kilometers, with a triggering threshold of ~0.07 megapascals. Although thousands of disposal wells operate aseismically, four of the highest-rate wells are capable of inducing 20% of 2008 to 2013 central U.S. seismicity.

An investigation of seismicity clustered near the Cordel Field, west central Alberta, and its relation to a nearby disposal well

AbstractHistorically, seismicity documented in the Western Canada Sedimentary Basin has been relatively quiescent and earthquakes are usually restricted to the foreland belt of the Rocky Mountains. However, exceptional clusters of events, which have remained active for decades, are recognized in Alberta. In this study we investigate the seismicity in this region using data obtained from recently established regional arrays, emphasizing the relationship between a disposal well in the Cordel Field and a nearby cluster of previously reported earthquakes. We explore temporal correlations of wastewater pumping rates and local seismic activity dating back to 1960. We find that the first statistically significant increase in seismicity lags the onset of wastewater injection (October 1991) by ~3.33 years. In particular, the waveform similarity of 32 events are analyzed from continuous data recorded at NOR, a nearby (~30 km) station operated by the University of Alberta starting in September of 2006. Results from this analysis suggest that many events are well correlated in the characteristics of the waveforms and thus are likely to share a similar origin and source mechanism. The most prolific of these multiplets repeats more than 10 times sporadically throughout the entire duration of recorded data from October 2006 to March 2012. Despite the limited availability of nearby stations, which adversely affects the resolution of our analysis, hypocenter depths could be relatively accurately determined from waveform synthesis and double difference methods. The results of our analysis provide first‐order evidence that the seismicity is consistent with fluid injection‐induced events.

Verification of sprayed clay technology with respect to the geological disposal of radioactive waste

The investigation of sprayed clay technology has been underway at the Josef Underground Laboratory for a number of years. This technology was developed principally with respect to the backfilling of shafts and galleries in deep repositories providing access to disposal wells containing high-level long-lived radioactive waste. At present research is being focused on the use of this technology to fill the space between the spent fuel container and the wall of the disposal well. This paper describes experience gained from the various stages of the research including the selection of a suitable spray material and the testing and modification of the equipment employed and presents the results of a selection of shot clay mixture tests. ARTICLE INFO

The 17 May 2012 M4.8 earthquake near Timpson, East Texas: An event possibly triggered by fluid injection

AbstractThis study summarizes our investigation of the 17 May 2012 MW‐RMT4.8 earthquake near Timpson, Texas, the largest earthquake recorded historically in eastern Texas. To identify preshocks and aftershocks of the 17 May event we examined the arrivals recorded at Nacogdoches (NATX) 30 km from the 17 May epicenter, at nearby USArray Transportable Array stations, and at eight temporary stations deployed between 26 May 2012 and mid‐2013. At NATX we identified seven preshocks, the earliest occurring in April 2008. Reliably located aftershocks recorded by the temporary stations lie along a 6 km long NW‐SE linear trend corresponding to a previously mapped basement fault that extends across the highest‐intensity (MMI VII) region of the 17 May main shock. Earthquakes in this sequence are relatively shallow—with focal depths ranging from 1.6 to 4.6 km. Evidence supporting these depths include: hypocentral locations of exceptionally well‐recorded aftershocks, S‐P intervals at the nearest stations, and comparisons of synthetics and observed seismograms. Within 3 km of the linear trend of aftershock activity there are two Class II injection disposal wells injecting at 1.9 km depth beginning in August 2006 and February 2007, with injection rates averaging 42,750 m3/mo and 15,600 m3/mo, respectively. Several observations support the hypothesis that fluid injection triggered the Timpson sequence: well‐located epicenters are situated near a mapped basement fault and near high‐volume injection wells, focal depths are at or below the depths of injection, and the earliest preshock (April 2008) occurred after the onset of injection in 2006.

Screening of advanced produced water treatment technologies: overview and testing results

Produced water (PW) is the highest volume liquid waste stream generated by the petroleum industry. Historically, the treatment of PW has been limited to free oil and suspended solids removal, using physical separation technologies, and injection in disposal wells. However, because of new regulations combined with geological restrictions and water scarcity, the drive to have greater fraction of the PW more extensively treated and ultimately reused is increasing. This paper presents the results of laboratory investigations carried out by the ConocoPhillips Global Water Sustainability Center, where various treatment processes (membrane processes, membrane bioreactors, membrane distillation and ozonation) were evaluated as treatment methods for PW from different oil & gas fields. The preliminary results of investigations performed confirmed the potential of Membrane Filtration, MBRs and Ozonation to treat PW and produce an effluent suitable for reuse. Membrane distillation may have potential in the longer term.

The geothermal potential of the basal clastics of Saskatchewan, Canada

The Winnipeg and Deadwood formations form deep clastic reservoirs in Saskatchewan, Canada, with temperatures exceeding 40 °C over most of southern Saskatchewan and reaching 100 °C in southwestern Saskatchewan. At these temperatures, the formations have geothermal potential for development of direct use and electricity generation systems. Numerous disposal wells operating at rates of 30 L/s or more are currently installed in these formations, suggesting that electricity could be generated at rates exceeding 2 megawatts of electrical output (MWe) from individual wells. These basal clastic units, thus, could provide significant energy supply over a broad region of Saskatchewan.

Offshore Water-Disposal Wells: Formation Damage and Treatment

This article, written by Dennis Denney, contains highlights of paper IPTC 16595, ’Formation Damage and Treatment of Offshore Water-Disposal Wells in Saudi Arabia: Case Studies,’ by Ken Mei, Hassan B. Qahtani, Abdulmohsen S. Al-Kuait, and Luai A. Sukkar, Saudi Aramco, prepared for the 2013 International Petroleum Technology Conference, Beijing, 26-28 March. The paper has not been peer reviewed. In one Saudi Aramco offshore oil field, the production from different platforms is transported to an onshore gas/oil-separation plant (GOSP) where the produced water is removed from the hydrocarbon stream. Then, the produced water is injected continuously into highly permeable formations through disposal wells. Therefore, the water-disposal system is an integral part of the hydrocarbon-recovery system. Failure of one of the disposal wells could affect oil production adversely. Introduction Field A is a mature oil field with more than 500 active producing wells, and it has been on stream for more than 50 years. The crude-oil-handling facility was built onshore with limited equipment capacity and a limited water-disposal capacity. The field produced formation water beginning in the 1980s, and the water cut has increased over time. This field is expected to continue operating at approximately full crude-oil-handling capacity, with all produced water to be dis-posed of continuously. The main focus is how to maintain the ability to dispose of all the produced water. Of the options studied, the best was to drill new water-disposal wells and to service existing disposal wells to maintain a high disposal capacity. Evaluation of the disposal capacity of each well is the core part of this option and is a major challenge associated with a water-disposal system. Well tests on water-disposal wells are uneconomical to conduct monthly. Also, water injection would have to be interrupted during testing. Another major challenge was determining an effective treatment for water-disposal wells that have encountered a significant drop in injection potential. The produced water contains a significant amount of waste material including solids, salts, chemicals, and residual oil. Even after being treated, the waste-water causes pipeline corrosion and formation damage. Conventional acidizing with hydrochloric acid (HCl) or mud acid (12% HCl+6% hydrofluoric acid) proved ineffective for treating the formation damage to improve injectivity. A new way was found for dealing effectively with injection loss caused by specific formation damage. Water-Disposal System The produced water passes through high- and low-pressure separators and then is pumped to the disposal wells by two injection pumps and a 24-in. above-ground pipeline. Because the water-disposal system is part of the hydrocarbon-recovery system, reduction of produced-water injection would restrict oil production. An increasing number of wells have electrical submersible pumps (ESPs) installed to produce fluid at higher rates, which accelerates water production. With new ESP wells coming on stream, in a few years the water volume will be two and one-half times the current produced-water volume.

Seeking Lower-Cost Ways To Deal With Fracturing Water

Unconventional Water The management of water used for fracturing oil and gas wells is all over the map. In Pennsylvania, most of the produced water is treated so it can be used again for fracturing, but some is cleaned to the point at which it meets the stringent requirements for river disposal. In Texas, fracturing fluids generally use fresh water, and what flows back to the surface is injected into a deep disposal well. A 2012 report, prepared by the Bureau of Economic Geology for the Texas Oil & Gas Association, titled Oil & Gas Water Use in Texas, puts the percentage of produced water recycled for fracturing in the Eagle Ford shale at 0%, and in the Permian Basin near Midland at 2%. In these arid regions fresh water is used by a wide margin. In the Eagle Ford, 20% of the water for fracturing came from brackish aquifers, and 30% in the Permian around Midland used water too salty to be potable. Things change fast in these booming plays. But the lead author of the report, Jean-Philippe Nicot, a research scientist at the Bureau of Economic Geology of The University of Texas at Austin, said: “I don’t think those numbers have changed much. There is likely some reuse/recycling in all plays, so 0% is probably not correct, but close to it.” For Michael Dunkel, director of sustainable development at Pioneer Natural Resources, past performance in places like the Permian is not a useful indicator of the future in an area where so many are looking for alternatives. “I am confident what we are seeing today is just at the starting gate and it will continue to evolve,” he said. Given the thousands of unconventional wells drilled, this may seem to be a slow evolution, but the staggering scale of these formations, particularly in the Permian, means operators such as Pioneer are just moving from scattered exploration drilling to concentrated development. “We will be drilling for 30-plus years out there,” Dunkel said. While he is confident the industry will change how it manages water for unconventional development, there are a lot of ways it can go from here. The decisions hinge on a complex mix of variables, which can be boiled down to a simple imperative: What is the lowest-cost option? The correct answers will vary from region to region, and from company to company depending on factors such as the scale of a company’s operation. Chesapeake Energy treats most of the water produced in its wells in Pennsylvania for reuse in fracturing with a small amount sent for disposal, said Rick McCurdy, manager of chemicals and water reclamation at Chesapeake Energy Corp. In south Texas most of the water is pumped from freshwater aquifers and produced water is injected into disposal wells.

Analysis of the Cleburne, Texas, Earthquake Sequence from June 2009 to June 2010

On 9 June 2009, an ![Graphic][1] 2.8 earthquake shook Cleburne, Texas, a community not known to have previously experienced earthquakes. Over 50 small earthquakes followed by the end of December 2009. A temporary network of four and then five IRIS‐Passcal broadband systems was deployed from June 2009 to June 2010, recording data that were used to locate 38 events with the most confident P ‐ and S ‐arrival picks. Event locations were distributed along a 2 km long north‐northeast trend. The location centroid was at 32.298° N, 97.372° W and at 3.6 km depth. This location is approximately 1.3 km from a saltwater disposal well that began injection in October 2007 and 3.2 km away from a second injection well that was active from September 2005 to late July 2009. Focal mechanisms estimated for the best‐recorded events suggest a north‐northeast–south‐southwest‐trending normal fault with a dip of ∼50° and a component of oblique motion (rake of ∼−80°). This average solution is generally consistent with the north‐northeast‐trending extensional faults that are prevalent across parts of Texas, Oklahoma, Louisiana, and Arkansas. Stress drops calculated from P and S spectra for seven different events ranged from 3.9 to 90 bars, with most estimates between 40 and 50 bars, typical values for intraplate earthquakes. Because there were no known previous earthquakes, and the located events were close to the two injection wells and near the injection depth, the possibility exists that earthquakes may be related to fluid injection. Online Material: Tables of absolute and relative earthquake locations and a figure summarizing focal mechanism solutions. [1]: /embed/inline-graphic-1.gif