Papers by Stephen Whitaker
Hydrocarbon Production from Shallow Marine Sandstones in the Mississippian Cypress Formation at Lawrence Field, Illinois
AAPG Bulletin, 1992
Maquoketa paleotopography key to reservoirs in western Illinois
Oil & Gas Journal, Aug 12, 1996
Shallow Silurian reservoirs in western Illinois have been a primary target for exploration since ... more Shallow Silurian reservoirs in western Illinois have been a primary target for exploration since the late 1950s. It was not until the discovery and development of Buckhorn Consolidated field in the early 1980s, however, that significant drilling efforts for Silurian reservoirs were focused on western Illinois. At Buckhorn, 1.7 million bbl of oil have been produced from a basal Silurian dolomite at about 650 ft. Drawn by inexpensive drilling and available acreage, hundreds of operators flocked to western Illinois to try their luck. By the late 1980s, however, exploration efforts in western Illinois were curtailed due to the failure to locate additional significant reservoirs. Much of this failure was due to the lack of a suitable geologic model that could be used to explain the reason for reservoir development and thereby guide exploration efforts. An article by Whitaker and Howard in 1995 presented a geologic model explaining Silurian reservoir development and stratigraphic entrapment of oil at Buckhorn Consolidated field were formed as Silurian dolomite in-filled a shallow paleovalley cut into the underlying Ordovician Maquoketa shale. Some companies have recently initiated new exploration efforts in the area using this model. This paper discusses the efforts and results of several of thesemore » new areas.« less
An Integrated Approach to Reservoir Characterization in the Illinois Basin: Multidisciplinary Studies
Cross section B-B', showing basal Pennsylvanian sandstone along the western side of the paleovall... more Cross section B-B', showing basal Pennsylvanian sandstone along the western side of the paleovalley 16 14 Cross section C-C, showing structural and stratigraphic relations of Chesterian and basal Pennsylvanian strata along the crest of the anticline 17 15 Cross section D-D', showing a relatively thick basal Pennsylvanian reservoir preserved along the western side of the paleovalley 18 16 Cross section E-E', a longitudinal section along the paleovalley showing the changing thickness of the basal Pennsylvanian reservoir across the Hardinville Anticline 19 17 Evolution of paleovalleys at the Mississippian-Pennsylvanian unconformity and subsequent sand bar deposition across the Hardinville Anticline
Waulsortian mound development in Warsaw at Broughton field, Ill
Oil & Gas Journal, Apr 17, 1995
Oil production in the Lower Mississippian Ullin (Warsaw) limestone was first established in Illin... more Oil production in the Lower Mississippian Ullin (Warsaw) limestone was first established in Illinois over 40 years ago. Exploration for hydrocarbons in this zone, however, was limited until recently due to a lack of a suitable explanation for reservoir development in this interval. The theory that Waulsortian mound development may explain many of these reservoirs was first presented in 1990. Research effort led by Zakaria Lasemi at the Illinois State Geological Survey has since established an excellent model for the generation of these bioherms. Lasemi performed numerous examinations of outcrops, cores, and well cuttings to develop his theory on the development and evolution of these biohermal features. This article presents an application of Lasemi`s model to an oil field in the Illinois basin. Similar applications could improve exploration and development success in Warsaw reservoirs.
An Integrated Approach to Reservoir Characterization in the Illinois Basin
The Mississippian Cypress Formation (Chesterian) is 1 00 feet thick at Bartelso Field and compris... more The Mississippian Cypress Formation (Chesterian) is 1 00 feet thick at Bartelso Field and comprises a section of shales and sandstones that has produced about 2.5 million barrels of oil from 76 wells since production first began in 1 936. The reservoir rocks are clean quartz arenites to subarkoses deposited under shallow marine conditions. Porosity ranges from 16% to 25%, and permeabilities range from 100 to about 500 millidarcies in the reservoir rocks. The Cypress Formation was subdivided into four intervals, each separated by shale layers. These four intervals were arbitrarily labeled, in ascending order, pink, purple, gray, and red. On the basis of wireline log correlations, subsurface mapping, and petrographic studies of well cuttings and core samples, the authors interpreted the environments of deposition for these intervals to be as follows: (1) pink intervalshallow subtidal influences in a delta-front setting; (2) purple intervalshoreface subjected to some tidal influence; (3) gray intervaltidal flat to lagoonal influences, possibly some lower coastal plain; and (4) red intervalupper shoreface subjected to strong tidal influences. These environments indicate that the pink, purple, and gray intervals were deposited in a prograding sequence, with the gray interval representing sediments deposited under the shallowest conditions. Sandstones within the red interval represent tidal ridges (tidal bars) formed in marine conditions during a transgressive phase that inundated the deltaic complex. Petrographic and mineralogic analyses revealed that silica is the primary cementing agent of Cypress sandstones at Bartelso. Most of the silica is in the form of quartz overgrowths, although minor amounts of chert are also present. Calcite cement is rare and is restricted to syntaxial cement around echinoderm fragments. Clay minerals constitute less than 2% of the total rock and comprise mainly kaolinrte with lesser amounts of chlorite, iron-rich chlorite, and illite. Porosity enhancement has resulted from the partial dissolution of potassium feldspars and calcium-rich plagioclases. Reservoir compartmentalization is a factor in recovery efficiency for the sandstones of the red interval. Currently, all sandstone reservoirs in Illinois are required to be developed on a 10-acre well spacing. The shingled bars separated by thin shales that characterize the red interval preclude effective drainage with a 1 0-acre spacing. The less heterogeneous sandstones within the purple and gray intervals, however, may be relatively well-drained by 1 0-acre well spacing. Sandstones within the pink interval contained no hydrocarbons at Bartelso, but correlative units may provide reservoirs in other areas of the basin.
Potential in sub-Devonian strata listed for Illinois, Kentucky, Indiana
Oil & Gas Journal - OIL GAS J, 1992
More than 4.2 billion bbl of oil have been produced in the Illinois basin since hydrocarbons were... more More than 4.2 billion bbl of oil have been produced in the Illinois basin since hydrocarbons were first discovered there more than 100 years ago. Roughly three-fourths of this production has come from 58 different pay zones in Illinois, but only four of these zones are in strata older than Devonian. Seismic data indicate that the sedimentary section may be aoubt 23,000 ft thick in the basin, yet there are no penetrations below 15,000 ft. The limited number of deep tests, coupled with the amount of sedimentary section that has not been contacted, translates to a vast volume of unexplored strata. This article discusses the potential for stratigraphic plays, structural plays, and source rocks in sub-Devonian strata of the Illinois basin. Although these discussions are based primarily on information form Illinois, they are applicable to the parts of the basin in Kentucky and Indiana as well.
Regional Cross Section Program for Illinois Basin: ABSTRACT
AAPG Bulletin, 1989
For the first time, the Illinois State Geological Survey will publish a network of regional cross... more For the first time, the Illinois State Geological Survey will publish a network of regional cross sections portraying the structural and stratigraphic framework of the entire Illinois basin. The network of 16 structural cross sections radiating outward from the Union Oil 1 Cisne Community well (Sec. 3, T1N, 7E, Wayne County, Illinois) will consist of wireline logs showing formation boundaries and gross lithofacies of the entire stratigraphic column for over 140 wells. Indiana and Kentucky portions of the network will be prepared in conjunction with their respective state geological surveys. Wireline logs are being digitized and stored to allow reproduction of log curves at different scales and in various combinations. Initial cross sections will be published at a vertical scale of 1 in. = 400 ft and a horizontal scale of 1 in. = 8 mi (1:500,000). To assure the most accurate structural and lithologic portrayals possible, numerous wireline logs are being examined in addition to the 140 illustrated on the sections. Available seismic data, sample and core descriptions, and existing structure, isopach, and facies maps are also being used. Text describing the sections will be included on each sheet. Topics will cover a brief history of deposition and structuralmore » evolution, distribution of source rocks, reservoir rocks and seals, and significant fields and plays.« less
Characteristics of Aux Vases and Cypress Reservoirs in Illinois
AAPG Bulletin, 1992
Northwest-southeast cross section along B-B' shows thinning of the upper sandstone interval of th... more Northwest-southeast cross section along B-B' shows thinning of the upper sandstone interval of the Aux Vases northwest of the field 10 Isopach map of clean sandstones within the upper sandstone interval of the Aux Vases Formation 1 1 Isopach map of clean sandstones within the lower interval of the Aux Vases Formation 1 12 SEM photomicrograph of diagenetic clay minerals on quartz grains and intermediate calcite cement 1 3 SEM photomicrograph of dissolved potassium feldspar with late stage hexagonal quartz overgrowths 14 Diagram of diagenetic sequence for the Aux Vases reservoir at Stewardson Field 15 Cumulative production by lease and initial production map 16 Drill stem test data map 17 Reservoir limit map 18 Production decline curve for Stewardson Field TABLE 1 Mineral analysis of the clay size particles PLATES 1 Photomicrograph of a sample from the Aux Vases Sandstone reservoir 2 Photomicrograph of exceptionally well preserved echinoderm columnal 1 3 Photomicrograph of several grains of feldspar in varying stages of dissolution 4 Photomicrograph of Archaeolithophyllum sp., a red alga found in car- bonate beds between the upper and lower sandstone intervals in Stewardson Field 1
Exploration for basal Silurian reservoirs in western Illinois
Oil & Gas Journal, Jul 31, 1995
The discovery of two oil fields, Kellerville and Siloam, in shallow (600--675 ft deep) basal Silu... more The discovery of two oil fields, Kellerville and Siloam, in shallow (600--675 ft deep) basal Silurian carbonates in 1958 and 1959 respectively, was the first new production in western Illinois since the discovery of the Devonian Hoing sandstone at Colmar-Plymouth field in 1914. A second, and more major, drilling boom in western Illinois resulted from official recognition in 1982 of a significant oil discovery in basal Silurian rocks at Buckhorn East oil field, later Buckhorn Consolidated. Within a relatively short time, numerous rigs were moving into western Illinois in the hopes of repeating the successes experienced at Buckhorn East. Unfortunately, there was no adequate geologic model that explained the oil accumulations in western Illinois. Basal Silurian reservoirs in western Illinois developed due to dolomitization of carbonate that filled shallow valleys incised in the underlying Maquoketa shale. Exploration for these reservoirs should utilize all of the clues that are presented here. It will be critical to continue gathering data from the area via quality wireline logs, cores, samples, and geophysical studies. It is unlikely that the Buckhorn-Siloam-Kellerville complex is unique in western Illinois.
AAPG Bulletin, 1989
FIGURES 1. Regional map showing Silurian reefs in Illinois 2. Silurian structure map at Marine Fi... more FIGURES 1. Regional map showing Silurian reefs in Illinois 2. Silurian structure map at Marine Field 3. Generalized stratigraphic column of southern Illinois 4. Schematic cross sections illustrating effects of differential compaction around a buried reef 6 5. Schematic cross section showing average density values of strata in and around the Silurian reef 7 6. Bouguer gravity anomaly map and structure map on the Ste. Genevieve Formation at Nashville Reef 8 7. Bouguer gravity anomaly at Marine Field 9 8. First order least squares trend surface at Marine Field 12 9. Residual Bouguer gravity anomaly surface at Marine Field 13 10. Second vertical derivative residual Bouguer gravity anomaly map at Marine Field 14 Digitized by the Internet Archive in 2012 with funding from
Fluvial-Estuarine Valley Fill at the Mississippian-Pennsylvanian Unconformity, Main Consolidated Field, Illinois
Casebooks in Earth Sciences, 1990
Approximately 4 billion barrels of oil (6.4 × 108 m3) have been produced in the Illinois basin si... more Approximately 4 billion barrels of oil (6.4 × 108 m3) have been produced in the Illinois basin since oil was discovered there more than a century ago (Fig. 13–1). Production has come largely from structural traps at depths of less than 5,500 feet (1,675 m) that collectively contain more than sixty different pay zones ranging in age from Ordovician to Pennsylvanian (Fig. 13–2). Despite the maturity of the basin, significant discoveries could come from numerous plays that remain to be tested.
Reservoir Potential in Lower Devonian Strata of Illinois: ABSTRACT
AAPG Bulletin, 1989
Lower Devonian strata have considerable potential for hydrocarbon reserves in the Illinois basin;... more Lower Devonian strata have considerable potential for hydrocarbon reserves in the Illinois basin; however, there has not yet been a major exploration effort for Lower Devonian reservoirs in the basin, nor has an adequate model been developed to explain distribution of these reservoirs. Due to the lack of exploration, production from these strata is presently limited to a few fields in south-central and southwestern Illinois. A review of data available at the Illinois State Geological Survey indicates that most Lower Devonian production in Illinois is from dolomitized cherty limestones in the Clear Creek Formation and Grassy Knob Chert. Minor production has also been noted in similar facies in the Bailey Limestone. Reservoir development within these strata is caused by dolomitization of slightly porous limestone beds and occurs in proximity to the beds' subcrop at the sub-Kaskaskia (pre-Middle Devonian) unconformity. The best reservoir development appears to be along paleotopographic highs on the Lower Devonian surface. Traps are most commonly formed where porous dolomitic beds, truncated at the sub-Kaskaskia unconformity are underlain by tight cherty limestones and overlain by tight Middle Devonian carbonates. Traps may also be formed downdip from porosity truncations where trends of porous Lower Devonian strata coincide with structuralmore » closures. The geometry and distribution of known reservoirs and traps in Lower Devonian carbonates indicate there may be several productive fairways in the basin. Exploration for and exploitation of these plays will depend on an increased understanding of Lower Devonian strata utilizing exploration models such as the one presented here.« less
AAPG Bulletin, 1987
New interpretations of subsurface data support the hypothesis that pinnacle reefs developed rando... more New interpretations of subsurface data support the hypothesis that pinnacle reefs developed randomly throughout a ramp environment that encompassed most of the Illinois Basin during the Silurian. Given this hypothesis, distribution of reefs would be widespread; thus exploration for hydrocarbons associated with Silurian reefs should not be limited to a commonly perceived "hingeline" trend. Well log correlations, core analyses, and sample descriptions indicate that Silurian pinnacle reefs first developed in Illinois during earliest Niagaran time. Reef development also began in Indiana at about this time when uplift of the Kankakee and Cincinnati Arches formed the Wabash Platform and altered the depositional setting of the proto-Illinois Basin to a ramp-platform during the early Niagaran. Pinnacle reefs continued to develop throughout the remainder of the Silurian along the middle ramp in Illinois and along the flanks of the Wabash Platform where they formed the Terre Haute and Fort Wayne Banks. Shorter pinnacle reefs and complex coalesced reefs formed along the upper ramp in Illinois and on the shallower portions of the platform in Indiana. Reef exposure at the Material Service Corporation's quarry, sec. 10, T38N-R12E, Cook County, Illinois. Note reef flank beds dipping away from the reef core. Because of pre-middle Devonian erosion of Silurian reefs in the northern half of Illinois, together with early dolomitization of Silurian strata, topographic expression of the reefs is less in this area than in southern Illinois. Very good potential-Reef structures are preserved because the Cayugan Bailey Formation shielded underlying strata from pre-Middle Devonian erosion. Oil and gas entrapment due to reefs is possible in porous reef rock or in strata draped over pinnacle reefs. Good potential-Upper Niagaran strata are eroded and dolomitized; reef structures are not evident. Oil and gas entrapment due to reefs is restricted to porous reef rock. Poor potential-Erosion and extensive dolomitization of relatively shallow Silurian reef, reef wash, and carbonate bank facies resulted in a widespread, blue-grey, vuggy dolomite that precludes oil and gas entrapment due to lack of lateral seals. Poor potential-Extensive erosion of dolomitized Silurian strata has removed pinnacle reef facies. Poor potential-Water too shallow for reef development Poor potential-Water too deep for reef development Outcrop of Silurian Silurian absent
A Comparison of Reservoir Heterogeneity and Recovery Efficiency of Two Offshore Bar Complexes in an Intracratonic Basin
AAPG Bulletin, 1991
ABSTRACT
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Papers by Stephen Whitaker