James A. Sorensen

Geologic Characterization of a Bakken Reservoir for Potential CO2 EOR

Copyright 2013, Unconventional Resources Technology Conference (URTeC) This paper was prepared for presentation at the Unconventional Resources Technology Conference held in Denver, Colorado, USA, 12-14 August 2013. The URTeC Technical Program Committee accepted this presentation on the basis of information contained in an abstract submitted by the author(s). The contents of this paper have not been reviewed by URTeC and URTeC does not warrant the accuracy, reliability, or timeliness of any information herein. All information is the responsibility of, and, is subject to corrections by the author(s). Any person or entity that relies on any information obtained from this paper does so at their own risk. The information herein does not necessarily reflect any position of URTeC. Any reproduction, distribution, or storage of any part of this paper without the written consent of URTeC is prohibited.

GAS INDUSTRY GROUNDWATER RESEARCH PROGRAM

The objective of the research described in this report was to provide data and insights that will enable the natural gas industry to (1) significantly improve the assessment of subsurface glycol-related contamination at sites where it is known or suspected to have occurred and (2) make scientifically valid decisions concerning the management and/or remediation of that contamination. The described research was focused on subsurface transport and fate issues related to triethylene glycol (TEG), diethylene glycol (DEG), and ethylene glycol (EG). TEG and DEG were selected for examination because they are used in a vast majority of gas dehydration units, and EG was chosen because it is currently under regulatory scrutiny as a drinking water pollutant. Because benzene, toluene, ethylbenzene, and xylenes (collectively referred to as BTEX) compounds are often very closely associated with glycols used in dehydration processes, the research necessarily included assessing cocontaminant effects on waste mobility and biodegradation. BTEX hydrocarbons are relatively water-soluble and, because of their toxicity, are of regulatory concern. Although numerous studies have investigated the fate of BTEX, and significant evidence exists to indicate the potential biodegradability of BTEX in both aerobic and anaerobic environments (Kazumi and others, 1997; Krumholz and others, 1996; Lovely and others, 1995; Gibson and Subramanian, 1984), relatively few investigations have convincingly demonstrated in situ biodegradation of these hydrocarbons (Gieg and others, 1999), and less work has been done on investigating the fate of BTEX species in combination with miscible glycols. To achieve the research objectives, laboratory studies were conducted to (1) characterize glycol related dehydration wastes, with emphasis on identification and quantitation of coconstituent organics associated with TEG and EG wastes obtained from dehydration units located in the United States and Canada, (2) evaluate the biodegradability of TEG and DEG under conditions relevant to subsurface environments and representative of natural attenuation processes, and (3) examine the possibility that high concentrations of glycol may act as a cosolvent for BTEX compounds, thereby enhancing their subsurface mobility. To encompass a wide variety of potential wastes representative of different natural gas streams and dehydration processes, raw, rich, and lean glycol solutions were collected from 12 dehydration units at eight different gas-processing facilities located at sites in Texas, Louisiana, New Mexico, Oklahoma, and Alberta. To generate widely applicable environmental fate data, biodegradation and mobility experiments were performed using four distinctly different soils: three obtained from three gas-producing areas of North America (New Mexico, Louisiana, and Alberta), and one obtained from a North Dakota wetland to represent a soil with high organic matter content.

SUBTASK 1.7 EVALUATION OF KEY FACTORS AFFECTING SUCCESSFUL OIL PRODUCTION IN THE BAKKEN FORMATION, NORTH DAKOTA PHASE II

Production from the Bakken and Three Forks Formations continues to trend upward as forecasts predict significant production of oil from unconventional resources nationwide. As the U.S. Geological Survey reevaluates the 3.65 billion bbl technically recoverable estimate of 2008, technological advancements continue to unlock greater unconventional oil resources, and new discoveries continue within North Dakota. It is expected that the play will continue to expand to the southwest, newly develop in the northeastern and northwestern corners of the basin in North Dakota, and fully develop in between. Although not all wells are economical, the economic success rate has been near 75% with more than 90% of wells finding oil. Currently, only about 15% of the play has been drilled, and recovery rates are less than 5%, providing a significant future of wells to be drilled and untouched hydrocarbons to be pursued through improved stimulation practices or enhanced oil recovery. This study provides the technical characterizations that are necessary to improve knowledge, provide characterization, validate generalizations, and provide insight relative to hydrocarbon recovery in the Bakken and Three Forks Formations. Oil-saturated rock charged from the Bakken shales and prospective Three Forks can be produced given appropriate stimulation treatments. Highly concentrated fracture stimulations with ceramic- and sand-based proppants appear to be providing the best success for areas outside the Parshall and Sanish Fields. Targeting of specific lithologies can influence production from both natural and induced fracture conductivity. Porosity and permeability are low, but various lithofacies units within the formation are highly saturated and, when targeted with appropriate technology, release highly economical quantities of hydrocarbons.

Subtask 2.2 - Creating A Numerical Technique for Microseismic Data Inversion

Geomechanical and geophysical monitoring are the techniques which can complement each other and provide enhancement in the solutions of many problems of geotechnical engineering. One of the most promising geophysical techniques is passive seismic monitoring. The essence of the technique is recording the acoustic signals produced in the subsurface, either naturally or in response to human activity. The acoustic signals are produced by mechanical displacements on the contacts of structural elements (e.g., faults, boundaries of rock blocks, natural and induced fractures). The process can be modeled by modern numerical techniques developed in geomechanics. The report discusses a study that was aimed at the unification of the passive seismic monitoring and numerical modeling for the monitoring of the hydraulic fracture propagation. The approach adopted in the study consisted of numerical modeling of the seismicity accompanying hydraulic fracture propagation and defining seismic attributes and patterns characterizing the process and fracture parameters. Numerical experiments indicated that the spatial distribution of seismic events is correlated to geometrical parameters of hydrofracture. Namely, the highest density of the events is observed along fracture contour, and projection of the events to the fracture plane makes this effect most pronounced. The numerical experiments also showed that dividing the totality of the events into groups corresponding to the steps of fracture propagation allows for reconstructing the geometry of the resulting fracture more accurately than has been done in the majority of commercial applications.

The Plains CO/sub 2/ reduction (PCOR) Partnership - identifying CO/sub 2/ sequestration opportunities for the cement industry in the central interior of North America

The Plains CO2 Reduction (PCOR) Partnership is one of seven regional partnerships established by the U.S. Department of Energy National Energy Technology Laboratory (NETL). The goal of the NETL regional partnerships program is to assess carbon sequestration opportunities that exist throughout the United States and Canada. The PCOR Partnership region covers an area of over 1.3 million square miles and includes nine states and three Canadian provinces. During Phase I activities, an inventory was made of the regions major stationary CO 2 sources, and many of the major geologic and terrestrial sinks were identified and characterized. The most likely sequestration options were matched to the CO2 produced by a given type of point source. Phase I activities identified thirteen cement/clinker production facilities located within the PCOR Partnership region. Collectively, they emit a total of approximately 12.5 million short tons of CO2/yr, which is 2.3% of the CO2 emitted from point sources in the region. Amine scrubbing currently offers the best near-term potential for effective separation of CO2 from cement kiln exit gases, with the cost of capturing and separating CO2 from cement kiln exit gases estimated to range from

ASSESSMENT OF THE SUBSURFACE FATE OF MONOETHANOLAMINE

41 to

Hydrocarbon Mobilization Mechanisms from Upper, Middle, and Lower Bakken Reservoir Rocks Exposed to CO

45/short ton. Compressing it to pipeline pressures costs about

Development of Storage Coefficients for Determining the Effective CO2 Storage Resource in Deep Saline Formations

9/short ton. The design and siting of cement production facilities should consider the possibility of CO2 capture and sequestration at some point in the future. While on the surface it may seem as if capture of CO2 from cement kilns will result in increased costs to the industry, it in fact may offer significant opportunities for development of new revenue streams, enhanced corporate image, new product development through attendant research and development, and potential efficiency gains in overall process operation

Field Test of CO2 Injection and Storage in Lignite Coal Seam in North Dakota

Burial of amine reclaimer unit sludges and system filters has resulted in contamination of soil at the CanOxy Okotoks decommissioned sour gas-processing plant with amines, amine byproducts, and salts. A three-phase research program was devised to investigate the natural attenuation process that controls the subsurface transport and fate of these contaminants and to apply the results toward the development of a strategy for the remediation of this type of contamination in soils. Phase I experimental activities examined interactions between monoethanolamine (MEA) and sediment, the biodegradability of MEA in soils at various concentrations and temperatures, and the biodegradability of MEA sludge contamination in a soil slurry bioreactor. The transport and fate of MEA in the subsurface was found to be highly dependant on the nature of the release, particularly MEA concentration and conditions of the subsurface environment, i.e., pH, temperature, and oxygen availability. Pure compound biodegradation experiments in soil demonstrated rapid biodegradation of MEA under aerobic conditions and moderate temperatures (>6 C). Phase II landfarming activities confirmed that these contaminants are readily biodegradable in soil under ideal laboratory conditions, yet considerable toxicity was observed in the remaining material. Examination of water extracts from the treated soil suggested that the toxicity is water-soluble. Phase II activities led to the conclusion that landfarming is not the most desirable bioremediation technique; however, an engineered biopile with a leachate collection system could remove the remaining toxic fraction from the soil. Phase III was initiated to conduct field-based experimental activities to examine the optimized remediation technology. A pilot-scale engineered biopile was constructed at a decommissioned gas-sweetening facility in Okotoks, Alberta, Canada. On the basis of a review of the analytical and performance data generated from soil and leachate samples, the biopile operation has successfully removed all identified amines and removed significant amounts of organic nitrogen and organic carbon. Salts initially present in the soil and salts generated during the biodegradation of contaminants remain to be flushed from the soil. Laboratory data show that these salts are readily removable with a simple soil leach.