Browsing by Subject "Water chemistry"

Now showing 1 - 5 of 5

Comparison of models for numerical simulation of low salinity waterflood
(2021-08-12) Santra, Ritabrata; Sepehrnoori, Kamy, 1951-; Delshad, Mojdeh
Accurately modeling Low Salinity Water Injection (LSWI) is essential for reliable predictions of oil recovery which affects exploration project planning and investment decisions. During LSWI, we modify the ions present in water before injection into an oil reservoir which helps maintain reservoir pressure and recover more oil from the reservoir, as compared to untreated regular water injection. Thus, understanding the primary mechanism and their effect of improved oil recovery due to wettability alteration during LSWI, and accurately modeling it, is essential to reliably predict and maximize oil recovery. However, there are several proposed models for numerical simulation of this novel method of LSWI and there exists no comparison for choosing the best model for an accurate simulation study. This study uses two simulators: (1) coupled reservoir simulator with geochemistry capabilities, UTCOMP-IPhreeqc and (2) commercial simulator, CMG’s GEM. We compare three models for numerical simulation of LSWI: (1) calcite dissolution, (2) total ionic strength, and (3) Extended Derjaguin, Landau, Verwey, and Overbeek (EDLVO). Most importantly, we also perform comparisons at both field and core scale. We describe the modeling capabilities of the two simulators and perform literature review to summarize the proposed mechanisms and the theory behind existing models. Finally, we simulate on (1) a synthetic carbonate field case, (2) a sandstone coreflood from a published literature, and (3) another sandstone coreflood, each with distinct mineralogy and petrophysical properties, to compare the three models. Results show that only the EDLVO model implemented in UTCOMP-Iphreeqc was able to accurately model the wettability alteration by estimating the change in contact angle during LSWI for all cases. While predicted recoveries from some of the models were similar, further investigation into the results uncovered the shortcomings of the other two models which resulted in incorrect calculation of the interpolating parameter. We concluded that the EDLVO model in UTCOMP-IPhreeqc works for all minerology while the other two models are scale, mineralogy, and case dependent. In future, we aim to develop a screening guide to choose model depending on the case, for simulating LSWI in commercial simulators which lack some of the mechanistic modeling capabilities of UTCOMP-IPhreeqc.
Geochemistry of ground water in the Miocene Oakville sandstone : a major aquifer and uranium host of the Texas coastal plain
(University of Texas at Austin. Bureau of Economic Geology, 1982) Henry, Christopher D.
The Oakville Sandstone is a major aquifer and a major host of uranium deposits in the Texas Coastal Plain. This report discusses the geochemistry - including major ions, the trace elements uranium, molybdenum, arsenic, and selenium, and oxidation-reduction potential - of Oakville ground water to evaluate the potential effect of uranium mining on water quality. Ground-water chemistry was investigated both regionally and in two major uranium mining districts. Major ion composition of Oakville ground water shows a regional variation. East Texas water has low to moderate dissolved solids (350 to 1,100 mg/L) and evolves from a calcium-magnesium-bicarbonate water in near-surface recharge areas to a sodium-bicarbonate composition downdip. The composition and evolution result from calcite solution and cation exchange. South Texas water has higher dissolved solids (up to 3,000 mg/ L) dominated by sodium, chloride, and sulfate. The high dissolved solids result from solution of evaporites within the Oakville and from the discharge along faults into the Oakville of high-dissolved-solids water from deeper aquifers. There are three oxidation-reduction zones within the Oakville: (1) an oxidizing zone with Eh values greater than 300 mV, controlled by the presence of measurable concentrations of dissolved oxygen, (2) an intermediate zone with Eh values between 110 and 10 mV, probably controlled by ferrous-ferric mineral reactions, and (3) a reducing zone with Eh values less than -40 mV, probably controlled by the presence of FeS2. Uranium, molybdenum, arsenic, and selenium show regional variations in concentrations, with trace element values in South Texas water distinctly higher than in East Texas water. The higher concentrations may result either from secondary dispersion from uranium deposits, which are more abundant in South Texas than in East Texas, or from a residual primary source in South Texas. Uranium closely follows behavior predicted from thermodynamic data; equilibrium with coffinite determines uranium concentrations in intermediate-Eh and reducing water. The other three elements do not follow predicted behavior, probably because no data are available on complexing. Analysis of water chemistry around the two uranium mining districts gives results similar to those found in the regional study. Very high concentrations of trace elements occur only in a few samples within ore zones. These high concentrations probably result from natural dispersal from the deposits, although this is not a widespread phenomenon.
Groundwater geochemistry and human ecology in the south Aegean : a diachronic investigation of the human–hydrologic relationship from prehistory to the present
(2016-08) Flood, Jonathan Michael; Luzzadder-Beach, Sheryl; Beach, Timothy P; Doolittle, William; Rosen, Arlene
This dissertation identifies and explores recurring patterns in the relationship between humans and hydrology. I explore both sides of the human-hydrologic relationship by highlighting (1) the principal modes used by humans to influence and augment the water cycle, and (2) the influence of water quantity and water chemistry on human affairs. The first theme is explored by charting the evolutionary trajectory of water management technology, beginning with the earliest known intentional manipulations of the water cycle roughly 10,000 years ago and ending with massive hydraulic projects of the present. This exposition reveals that across cultural, environmental, and temporal boundaries water management technology has progressed from simple techniques and devices to complex hydraulic installations in a series of incremental innovations, not in great leaps forward. A better understanding of water management’s origins and characteristic modes of innovation may encourage robust and farsighted hydrologic developments in a future of increased freshwater scarcity. The second theme investigates the influence of water quantity and water chemistry on: (a) settlement location and land-use strategies; (b) site tenure, especially during periods of climatic variability/change; (c) water-ritual and environmental perceptions; and (d) the formation and political ecology of early states. Methods and tools from geomorphology, hydrogeology, and environmental chemistry are used to define the complete physiochemical parameters of water resources in several study watersheds in the Eastern Mediterranean. Human-environmental behaviors captured in the archaeological and historical records were used to identify recurring patterns of human interaction with specific components of hydrologic systems. Several case studies demonstrate remarkable human sensitivity to geochemical differences in the natural environment. Ritual activity around several of these water sources seems to transcend time and cultural background. Conversely, other case studies demonstrate how cultures have repeatedly engineered the environment to manage and mitigate inherently poor or anthropogenically compromised water resources. This dissertation reveals the profound impacts humans have had on hydrologic systems and the way water’s chemical character and physical abundance have influenced human affairs.
Hydrochemical facies in the badwater zone of the Edwards Aquifer, central Texas
(1989) Clement, Tonia Judith, 1944-; Sharp, John Malcolm, Jr., 1944-
The Cretaceous Edwards and Georgetown Formations and their stratigraphic equivalents form two extensive carbonate aquifers in central Texas. These faulted, cavernous, and highly transmissive formations are the sole source of water for many communities, including the City of San Antonio. At the badwater line, which delineates a hydrogeologic boundary from 1 to 21mi (2-34km) south and east of the outcrop, the total dissolved solids concentration of the groundwater changes abruptly from less than 500 mg/l to over 1000 mg/l. Although the boundary is relatively stable, some water from the badwater zone migrates updip toward major springs and well fields. Unlike the water in the freshwater zone which is predominantly Ca-HCO₃, the chemistry of the badwater zone changes along the strike of the aquifer. From west to east, the first hydrochemical facies is Ca-SO₄ with a low chloride concentration. Faulting is minimal, and chlorides previously trapped in the pores or adsorbed by the carbonates have been flushed. This facies is produced by the dissolution of anhydrite in the badwater zone. As the potentiometric surface declines and the intensity of faulting increases to the east, sodium and chloride concentrations also rise. The hydrochemical facies changes first to Ca-Mg-SO₄ with high sodium and chloride concentrations and then, in the area of maximum faulting, to Na-Cl with calcium, magnesium, and sulfate subordinate. Using PHREEQE computer modeling, the second facies can be simulated by mixing fresh water with a Na-Ca-Cl oilfield brine and saturating it to specific states with calcite, dolomite, and gypsum. The origin of the Na-Cl facies with Na/Cl molar ratios close to one is still problematical. The fourth hydrochemical facies borders the northern segment of the aquifer and is predominately a Na-Cl-SO₄-HCO₃ water, the anions being approximately coequal in milliequivalents per liter. This last facies is almost identical to groundwaters in the underlying Trinity Group which probably have provided some recharge to the aquifer. Leakage from the Trinity Group or updip migration of bad water also may affect the quality of fresh water in this area
Lithium, boron, and barium in formation waters and sediments, Northwestern Gulf of Mexico Sedimentary Basin
(1989) Macpherson, Gwendolyn Lee, 1953-; Land, Lynton Stuart
Lithium, boron and barium, found in varying abundances in formation waters of the Gulf of Mexico Sedimentary Basin (Gulf Basin), have contrasting origins and are useful in assessing the open or closed nature of hydrocarbon-producing aquifers in Texas and Louisiana. Dissolved barium concentrations are controlled primarily by barite. Barium contents of sandstones show that either the barium content of dissolved or albitized detrital feldspars was considerably higher than in detrital feldspars which remain unaltered or that the original feldspar content of the sandstones was higher than that of the least altered sandstone analyzed. Boron and lithium contents are more difficult to attribute to local diagenesis. Most formation waters contain low concentrations of lithium (less than 10 mg/L) ascribable to feldspar diagenesis, except that whole-rock sandstones increase in lithium content with increasing diagenetic alteration. Formation waters from deep reservoirs contain very high concentrations of lithium for which there is no apparent local source. These waters do not resemble waters residual from either marine or non-marine evaporite deposition. Boron in most formation waters cannot originate exclusively from organic matter unless organic matter contents are much higher than have been measured, nor does it come from volcanic sediments because these are abundant only in the South Texas region while high boron contents are not geographically restricted. Formation waters from deep reservoirs contain very high concentrations of boron which probably come from deeper in the Basin because clay minerals, the major reservoir of boron, show no systematic decrease in boron content with depth. The 𝛿¹¹B of these waters is light (to +11%₀) and shows that the boron is not seawater boron (+40%₀) or boron from Jurassic evaporites (+31%₀). The 𝛿¹¹B of other formation waters lies between the value for sea water and the light boron. The Gulf Basin is nearly open with respect to lithium and boron but closed with respect to barium. The high concentrations of lithium and boron probably originate deeper than the sampled part of the Gulf Basin and may be products of metamorphic processes. The source of the barium in formation waters is detrital feldspars.