Browsing by Subject "Sandstone"
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Item A petrographic study of the subsurface Gallup Sandstone of San Juan County, New Mexico(Texas Tech University, 1956-08) Williams, Jack R.Recent exploration by petroleum companies has resulted in renewed interest in the subsurface Gallup Sandstone of the San Juan Basin, New Mexico. The present study provides detailed petrographic descriptions of samples from six wells and interpretation of the data obtained. Locations of the six wells are such that they follow the line of strike of the formation, and lithologies are similar at all locations. Quartz is the predominant mineral in all cases, with cacite being the most important cementing agent. The sporadic occurrence of siliceous cement is fre31quent enough to present a factor for consideration in any program of rock treatment for the purpose of increasing permeability. The most favorable area for additional exploration is believed to be to the south and southwest of the line of wells studied.Item A study of Pennsylvanian-Permian arkoses in north-central New Mexico(Texas Tech University, 1950-05) Butler, RoyNot availableItem Characterization and prediction of reservoir quality in chlorite-coated sandstones : evidence from the Late Cretaceous Lower Tuscaloosa Formation at Cranfield Field, Mississippi, U.S.A.(2013-05) Kordi, Masoumeh; Fisher, W. L. (William Lawrence), 1932-; Hovorka, Susan D. (Susan Davis)The effectiveness of CO₂ injection in the subsurface for storage and EOR are controlled by reservoir quality variation. This study determines the depositional processes and diagenetic alterations affecting reservoir quality of the Lower Tuscaloosa Formation at Cranfield Field. It also determines the origin, time and processes of the grain-coating chlorite and its impacts on reservoir quality. Moreover, by integrating depositional and diagenetic characteristics and by linking them to sequence stratigraphy, the distribution of reservoir quality, could be predicted within a sequence stratigraphic framework. The studied sandstones are composed of medium to coarse-grained, moderately sorted litharenite to sublitharenite with composition of Q76.1F0.4L23.5. Depositional environment of this formation in the Mississippi Interior Salt Basin is interpreted as incised-valley fluvial fill systems. The cross sections and maps at the field show trend of the sandy intervals within channels with a NW-SE paleocurrent direction. During burial of the sandstones, different digenetic alterations including compaction, dissolution, replacement and cementation by chlorite, quartz, carbonate, kaolinite, titanium oxides, pyrite and iron-oxide modified the porosity and permeability. Among these, formation of chlorite coats plays the most important role in reservoir quality. The well-formed, thick and continuous chlorite coatings in the coarser grain sandstones inhibited formation of quartz overgrowth, resulted in high porosity and permeability after deep burial; whereas the finer grain sandstones with the poorly-formed, thin and discontinuous chlorite coatings have been cemented by quartz. The optimum amount of chlorite to prevent formation of quartz overgrowths is 6% of rock volume. The chlorite coats are composed of two layers including the inner chlorite layer formed by transformation of the Fe-rich clay precursors (odinite) through mixed-layer clays (serpentine-chlorite) during early eodiagenesis and the outer layer formed by direct precipitation from pore waters through dissolution of ferromagnesian rock fragments during late eodiagenesis to early mesodiagenesis. In the context of the reservoir quality prediction within sequence stratigraphic framework, the late LST and early TST are suitable for deposition of chlorite precursor clays, which by progressive burial during diagenesis could be transformed to chlorite, and thus results in preserving original porosity and permeability in deep burial.Item Chemical and mechanical diagenetic evolution of deformation bands in sandstone(2016-08) O'Brien, Casey Megan; Eichhubl, Peter; Behr, Whitney; Gulick, SeanDeformation bands are zones of localized compaction, dilation, or shear in porous or granular sediments or sedimentary rock. Deformation bands are generally characterized by reduced permeability for cross-band fluid flow and increased capillary resistance for multi-phase flow, thus acting as barriers or baffles to fluid flow at an outcrop- to reservoir-scale. Deformation bands undergo increased lithification due to enhanced compaction and cementation, despite experiencing the same burial and temperature history as their host sandstone. I test the hypotheses that enhanced cementation in deformation bands is controlled by 1) the time between formation of the deformation band and onset of exhumation; 2) the degree of grain size reduction and thus the amount of fresh surface area available for quartz nucleation; 3) the amount of pore space available for pore-filling quartz cement; or a combination of these. I also evaluate possible links between mechanical deformation and chemical diagenesis in the context of tectonic setting and hostrock composition. To test these hypotheses, I reconstructed the structural and diagenetic evolution of deformation bands formed in the Jurassic Entrada, Navajo, and Wingate Sandstones in a contractional tectonic setting in the San Rafael monocline, and in the Entrada Sandstone in an extensional tectonic setting in the San Rafael Desert, Utah. I combined field-scale observations including band orientation, mutual crosscutting relations, and kinematic interpretations with petrographic point-count analyses using images obtained by high-resolution scanning electron microscopy. Based on structural criteria, I observed as many as six band generations. Younger generations of bands generally experience more cementation and porosity loss than older bands. I have identified that cataclasis is the dominant control over the amount of quartz cementation in bands of a similar lithology and burial history, as opposed to the time between band formation and exhumation, or available pore space. Within the same generation of bands, bands with more slip have more quartz cement. These findings highlight the importance of mechanical deformation in chemical diagenetic processes in sandstone. I find that the degree of cataclasis and quartz cementation does not differ between contractional and extensional tectonic settings, and that the hostrock compositional differences between the sandstones in this study do not cause significant differences in band diagenetic evolution.Item Development of a chemical treatment for condensate blocking in tight gas sandstone(2011-05) McCulley, Corey Alan; Pope, Gary A.; Sharma, Mukul M.Gas wells suffer a decrease in productivity because of the formation of a liquid hydrocarbon “condensate” in the near wellbore area. This "condensate" forms near producing wells when the flowing pressure is below the reservoir fluid's dew point. Several methods have been shown to temporarily alleviate this problem, but eventually the condensate bank reforms and the productivity again decreases. The use of surfactants to alter the near wellbore wettability to neutral wetting is a potential longer term solution to liquid blocking in these reservoirs. This alteration increases the gas and liquid relative permeabilities and thereby the productivity by reducing the residual liquid saturation. This enhancement allows the accumulated liquid to flow and is durable as long as the wettability alteration is persistent. This solution has been shown to be successful through core flood experiments and field trials in high permeability sandstones, but no improvements had been observed in low permeability cores. As the global demand for energy increases, the petroleum industry has begun to develop unconventional (low permeability) assets, new techniques are needed to maintain and improve their productivity. Liquid blocking in these wells can have a much larger impact on both the gas and condensate production in such low permeability formations. Applying this technique increases both gas and condensate mobility and should increase the economic producing life of these wells. Core flood experiments were conducted to investigate the ability of a chemical treatment to alter the wettability of low permeability sandstones. Previous experimentation did not find any improvement because the increased capillary forces prevented the treatment solution from being easily displaced. This concealed the benefit achieved when the wettability was altered. These experiments recorded smaller relative permeability increases compared to higher permeability core floods, so super critical carbon dioxide was tested as an alternative solvent. While the new treatment was more injectable, it was not as successful at altering wettability. Progress has been made on a solution to liquid blocking in low permeability sandstones, but additional research needs to be completed to further optimize this method.Item Fine scale sandstone acidizing coreflood simulation(2004) Li, Chunlou; Hill, A. D., (A. Daniel)Contrary to the traditional understanding of matrix acidizing of sandstone that the acid front propagates in the formation with a piston-like style, some wormhole like structures were observed in lab tests under certain conditions. Most current models treat the rock as a homogeneous porous medium to describe the matrix acidizing in sandstone. The most sophisticated design models divide the formation into a series of layers with constant properties (minerals, permeability, etc.) in each layer. However, sandstones invariably have small – scale heterogeneities in minerals and flow properties that may cause the effects of injected acids to differ greatly from what is predicted by a model based on a homogeneous formation. A fine-scale model of the sandstone core acid flooding is developed based on mass balance and the chemical reactions between acids and minerals that occur during sandstone acidizing. This mathematical model is numerically solved to predict the permeability response and demonstrate the distributions of acids, precipitates, flow velocity and porosity in the core during acidizing. Cores are divided into 8000 grid blocks to simulate the fine-scale structure of sandstone. Using standard geostatistical techniques at the beginning of simulations can generate heterogeneous porosity or/and minerals. The permeability response to acidizing is predicted using a model in which not only the porosity, but also the minerals, tortuosity, and statistical parameters of the particle size are considered. Application of the new model to typical acidizing conditions shows that acid tends to channel through a heterogeneous sandstone, with the most efficient acidizing occurring when the rock has a layered structure. A layered structure is simulated by assuming a correlated permeability field in the main flow direction, as occurs in sandstones having horizontal laminations. The model shows that acid can stimulate the matrix permeability two to three times farther into the rock than would be predicted with a standard acidizing model, which takes the rock as homogeneous porous medium.Item Regional character of the lower Tuscaloosa formation depositional systems and trends in reservoir quality(2012-12) Woolf, Kurtus Steven; Wood, Lesli J.For decades the Upper Cretaceous Lower Tuscaloosa Formation of the U.S. Gulf Coast has been considered an onshore hydrocarbon play with no equivalent offshore deposits. A better understanding of the Lower Tuscaloosa sequence stratigraphic and paleogeographic framework, source-to-sink depositional environments, magnitude of fluvial systems, regional trends in reservoir quality, and structural influences on its deposition along with newly acquired data from offshore wells has changed this decades-long paradigm of the Lower Tuscaloosa as simply an onshore play. The mid-Cenomanian unconformity, underlying the Lower Tuscaloosa, formed an extensive regional network of incised valleys. This incision and accompanying low accommodation allowed for sediment bypass and deposition of over 330 m thick gravity-driven sand-rich deposits over 400 km from their equivalent shelf edge. Subsequently a transgressive systems tract comprised of four fluvial sequences in the Lower Tuscaloosa Massive sand and an overlying estuarine sequence (Stringer sand) filled the incised valleys. Both wave- and tide-dominated deltaic facies of the Lower Tuscaloosa are located at the mouths of incised valleys proximal to the shelf edge. Deltaic and estuarine depositional environments were interpreted from impoverished trace fossil suites of the Cruziana Ichnofacies and detailed sedimentological observations. The location and trend of valleys are controlled by basement structures. Lower Tuscaloosa rivers were 3.8m – 7.8m deep and 145m – 721m wide comparable to the Siwalik Group outcrop and the modern Missouri River. These systems were capable of transporting large amounts of sediment indicating the Lower Tuscaloosa was capable of transporting large amounts of sediments to the shelf edge for resedimentation into the deep offshore. Anomalously high porosity (>25%) and permeability (>1200md) in the Lower Tuscaloosa at stratigraphic depths below 20,000 ft. are influenced by chlorite coating the detrital grains. Chlorite coatings block quartz nucleation sites inhibiting quartz cementation. Chlorite coats in the Lower Tuscaloosa are controlled by the presence and abundance of volcanic rock fragments supplying the ions needed for the formation of chlorite. Chlorite decrease to the east in sediments derived from the Appalachian Mountains. An increase in chlorite in westward samples correlates with an increase of volcanic rock fragments derived from the Ouachita Mountains.Item Sequence stratigraphic analysis of marginal marine sabkha facies : Entrada Sandstone, Four Corners region(2010-08) Makechnie, Glenn Kenneth; Kocurek, Gary; Mohrig, Davis; Steel, RonaldThe Middle Jurassic Entrada Sandstone of the Four Corners region, USA, is composed predominantly of very fine-grained, red, silty sandstone with poorly defined sedimentary structures. The origin of this facies is enigmatic, even though it is common both on the Colorado Plateau and globally, and is spatially situated between deposits recording unambiguous marine and aeolian environments. Eleven sections were measured along an 85 km transect from the Blanding Basin in southeastern Utah to the San Juan Basin in northwestern New Mexico. Outcrop and laboratory analyses distinguish eight facies: (1) silty shale, (2) shallow subaqueous reworked, fine- to medium-grained sandstone, (3) brecciated, very fine-grained sandstone, (4) crinkly laminated, very fine-grained sandstone with preserved wind ripples and abundant silty laminae, (5) weakly laminated, fine-grained sandstone with occasional silty laminae, (6) planar-laminated, fine-grained, wind-rippled sandstone, (7) cross-stratified, fine- to medium-grained aeolian cross-stratified sandstone, and (8) micritic limestone. Lateral and vertical relationships of these facies show a proximal to distal transition from cross-bedded wind-lain facies to loess-dominated sabkha facies with increasing abundance of water-lain facies basinward. The well known Todilto Limestone (facies 8) is situated stratigraphically below loess-dominated sabkha facies (facies 4 and 5) within the Entrada Sandstone, reinforcing previous interpretations that the unit represents a catastrophic flooding event and not a local groundwater flux.Item Sequence stratigraphy and depositional systems in the Upper Cretaceous (Cenomanian) Woodbine Group, Anderson and Cherokee Counties, Texas(2016-08) Krueworramunee, Kullamard; Fisher, W. L. (William Lawrence), 1932-; Ambrose, William A.; Mohrig, DavidThe Woodbine Group of the East Texas Basin has attracted considerable interest because of its remaining petroleum resource in the deeper Woodbine pay. Recent estimate of the remaining petroleum resources in the East Texas field is approximately 1.58 billion stock tank barrels (BSTB) (Wang et al., 2008). However, expected ultimate recovery is limited by reservoir compartmentalization controlled by a complex stratigraphic framework. The purpose of this study is to define depositional systems and construct the stratigraphic framework of the Woodbine Group in Anderson and Cherokee Counties to provide the geologic context for characterizing remaining reserves. This study integrates core data and log data from closely spaced wireline logs (~1000 wells), using a chronostratigraphic method, to define sequence stratigraphic units. The stratigraphic framework of the Woodbine succession in the study area is composed of a maximum of 14 cycles in the basin axis, decreasing to a minimum of 3 cycles eastward to the Sabine Uplift and a minimum of 6 cycles westward to the out crop belt. The Woodbine succession is overlain by impermeable deposits of the Eagle Ford Shale and the Austin chalk as hydrocarbon seals. The complexity and heterogeneity of sandstone bodies in the Woodbine Group are largely controlled by depositional origin. Woodbine highstand and lowstand sequences display great variations in the depositional systems. The highstand deposits are composed mostly of fluvial dominated delta deposits that consist of distributary-channel, crevasse-splay, and delta-front deposits. Gamma-ray and spontaneous potential responses for these highstand deposits are upward-coarsening and serrate. In contrast, Woodbine lowstand deposits are mainly composed of coarse-grained sandstones of incised valley fills, reflecting relative base-level fall. These lowstand deposits, truncate older highstand deposits and are inferred from planar-based and blocky serrate log responses. Furthermore, highstand and lowstand deposits are overlain by transgressive deposits. These transgressive deposits are characterized by upward-fining log response, reflecting relative base-level rise. Correlation of sequence stratigraphic surfaces, sandstone-body stacking patterns and reservoir complexity inferred from gross-sandstone maps can lead to new exploration targets in the Woodbine Group in the southern part of the East Texas Basin.Item Subsurface investigation of the Pennsylvanian cross cut sandstone, TWP and Busher fields, Runnels County, Texas(Texas Tech University, 1995-05) Henderson, Steven KirkThe Upper Pennsylvanian (Missourian) Cross Cut sandstone of the TWP and Busher fields. Runnels County, Texas, is an example of the smaller hydrocarbon plays that are receiving increased attention in west- and north-central Texas. An understanding of the distributions and reservoir characteristics of these plays is necessary for ensuring the success of future exploration and development strategies. Sediment characteristics, petrophysical log responses, and sand body geometry of the TWP and Busher Cross Cut sandstone reflect deposition in a distal prograding delta environment. Gross sand isopach mapping reveals a strikeoriented sand body approximately three miles in length and one-half mile in width. These attributes are similar to characteristics of the Cross Cut sandstone in other Pennsylvanian fields, and support a delta-front interpretation. Delta-front sandstones of the TWP and Busher fields represent a southwestern distal extension of the Eastland Delta system. Log responses and sand body geometry may be employed to infer the position of distributary mouth bar and channel facies associated with the delta-front sands. Sediments of the Cross Cut sandstone were exposed to a variety of diagenetic processes that influenced the evolution and preservation of porosity and permeability within the reservoir. Early development of epitaxial quartz overgrowths significantly decreased depositional porosity. Replacive calcite may also have decreased primary porosity; however, the dissolution of this calcite produced minor amounts of secondary porosity. Late-stage diagenetic processes, including precipitation of kaolinite and ankerite cements, further occluded porosity. The types, abundances, and morphologies of clay minerals, especially kaolinite and chlorite, within the Cross Cut sandstone may influence reservoir quality, in addition to reducing initial reservoir porosity and permeability. Interaction of these clays with fluids introduced during drilling, completion, and production may cause dispersion and migration of fines and precipitation of insoluble compounds, further occluding effective porosity and decreasing permeability. Petrophysical and volumetric evaluation of the TWP and Busher Cross Cut reservoir reveals estimated recoverable reserves of 763,997 stock tank barrels of oil. Since the discovery of the Busher Field in 1956, both fields haveproduced a combined total of approximately 629,667 barrels of oil. The Cross Cut sandstone within the TWP and Busher fields is an essentially depleted reservoir.