John H. Doveton

Flow unit modeling and fine-scale predicted permeability validation in Atokan sandstones: Norcan East field, Kansas

Characterizing the reservoir interval into flow units is an effective way to subdivide the net-pay zone into layers for reservoir simulation. Commonly used flow unit identification techniques require a reliable estimate of permeability in the net pay on a foot-by-foot basis. Most of the wells do not have cores, and the literature is replete with different kinds of correlations, transforms, and prediction methods for profiling permeability in pay. However, for robust flow unit determination, predicted permeability at noncored wells requires validation and, if necessary, refinement. This study outlines the use of a spreadsheet-based permeability validation technique to characterize flow units in wells from the Norcan East field, Clark County, Kansas, that produce from Atokan aged fine- to very fine-grained quartzarenite sandstones interpreted to have been deposited in brackish-water, tidally dominated restricted tidal-flat, tidal-channel, tidal-bar, and estuary bay environments within a small incised-valley-fill system. The methodology outlined enables the identification of fieldwide free-water level and validates and refines predicted permeability at 0.5-ft (0.15-m) intervals by iteratively reconciling differences in water saturation calculated from wire-line log and a capillary-pressure formulation that models fine- to very fine-grained sandstone with diagenetic clay and silt or shale laminae. The effectiveness of this methodology was confirmed by successfully matching primary and secondary production histories using a flow unit-based reservoir model of the Norcan East field without permeability modifications. The methodologies discussed should prove useful for robust flow unit characterization of different kinds of reservoirs.

Textural and pore size analysis of carbonates from integrated core and nuclear magnetic resonance logging: An Arbuckle study

AbstractThe T2 relaxation times recorded by nuclear magnetic resonance (NMR) logging are measures of the ratio of the internal surface area to volume of the formation pore system. Although standard porosity logs are restricted to estimating the volume, the NMR log partitions the pore space as a spectrum of pore sizes. These logs have great potential to elucidate carbonate sequences, which can have single, double, or triple porosity systems and whose pores have a wide variety of sizes and shapes. Continuous coring and NMR logging was made of the Cambro-Ordovician Arbuckle saline aquifer in a proposed CO2 injection well in southern Kansas. The large data set gave a rare opportunity to compare the core textural descriptions to NMR T2 relaxation time signatures over an extensive interval. Geochemical logs provided useful elemental information to assess the potential role of paramagnetic components that affect surface relaxivity. Principal component analysis of the T2 relaxation time subdivided the spectrum in...

Distribution and characteristics of a Middle Ordovician oolitic ironstone in northeastern Kansas based on petrographic and petrophysical properties: a Laurasian ironstone case study

Abstract The margins of Gondwana are generally considered to be the major sites of oolitic ironstone production during the Ordovician, and appear to be linked with global eustatic sea-level rise. Occurrences of oolitic ironstones within the North American craton are less well documented, but provide important supplementary data. The low latitude of Laurasia contrasted with Gondwana allows useful comparisons of climatic and temporal patterns of Ordovician ironstone formation. Middle Ordovician ironstones occur in siliciclastic sequences in the American mid-continent and appear to become progressively younger as the epicontinental sea advanced from the southwest across a predominantly carbonate terrain. In northeastern Kansas, the regional distribution pattern of primary, syndiagenetic goethite iron oolites within the St. Peter Sandstone indicate deposition peripheral to a north-northeast-trending chain of islands underlain by predominantly granitic rocks, located along an ancestral Nemaha uplift. Detailed compositional mapping in the subsurface was made possible by the distinctive petrophysical properties of the goethite zone and the extensive regional control of wireline-logged exploration wells. Petrographic data from ironstone core- and drill-cuttings both validate log analysis and give insights on possible modes of genesis. We propose that eustatic changes in sea level were the primary factor governing the formation and observed distribution patterns of the oolite bed(s). The relationship of the observed occurrence patterns to major rift-related faults of the Central North American Rift system suggests that synsedimentary tectonism also influenced this process. The most likely source of iron appears to be by derivation from intensive, humid weathering of granite exposed extensively on the ancestral Nemaha uplift archipelago.

Interpretation of lithologies and depositional environments of Cretaceous and Lower Permian rocks by using a diverse suite of logs from a borehole in central Kansas

As part of an extensive research program, a borehole was drilled to extend sedimentary facies models of the Cretaceous into the subsurface on the eastern side of the western interior Cretaceous basin in Kansas. Lithodensity-neutron and spectral gamma-ray logging runs were completed to facilitate interpretation of rocks penetrated by the borehole. Th/K, Th/U, and composition profile logs based on apparent grain density and photoelectric absorption index were prepared and used to show vertical changes in geochemical facies and clay mineralogy. These logs were compared with the gamma-ray log and drill cuttings to interpret depositional environments. The Th/K log sharply defines the Cretaceous/Permian boundary and, together with the Th/U log, emphasizes the contrast between marine Upper Cretaceous rocks of the Greenhorn depositional cycle and nonmarine to transitional rocks of the Lower Cretaceous. The long-term cyclic pattern of the Th/U log is an excellent indicator of a broad transgression/regression during the Greenhorn cycle on an open marine shelf, whereas extreme fluctuations of Th/U in the Lower Cretaceous rocks suggest a high degree of short-term environmental variability. Interpretation of the RHOMAA-UMAA compositional profile in the Dakota Formation indicates several pulses of marine transgression and regression prior to the initiation of the Greenhorn cycle in central Kansas.

Integrated core-log petrofacies analysis in the construction of a reservoir geomodel: A case study of a mature Mississippian carbonate reservoir using limited data

Small independent operators produce most of the Mississippian carbonate fields in the United States mid-continent, where a lack of integrated characterization studies precludes maximization of hydrocarbon recovery. This study uses integrative techniques to leverage extant data in an Osagian and Meramecian (Mississippian) cherty carbonate reservoir in Kansas. Available data include petrophysical logs of varying vintages, limited number of cores, and production histories from each well. A consistent set of assumptions were used to extract well-level porosity and initial saturations, from logs of different types and vintages, to build a geomodel. Lacking regularly recorded well shut-in pressures, an iterative technique, based on material balance formulations, was used to estimate average reservoir-pressure decline that matched available drillstem test data and validated log-analysis assumptions.Core plugs representing the principal reservoir petrofacies provide critical inputs for characterization and simulation studies. However, assigning plugs among multiple reservoir petrofacies is difficult in complex (carbonate) reservoirs. In a bottom-up approach, raw capillary pressure (Pc) data were plotted on the Super-Pickett plot, and log- and core-derived saturation-height distributions were reconciled to group plugs by facies, to identify core plugs representative of the principal reservoir facies, and to discriminate facies in the logged interval. Pc data from representative core plugs were used for effective pay evaluation to estimate water cut from completions, in infill and producing wells, and guide-selective perforations for economic exploitation of mature fields.The results from this study were used to drill 22 infill wells. Techniques demonstrated here can be applied in other fields and reservoirs.

KOALA--Minicomputer Log Analysis System for Geologists: ABSTRACT

An interactive computer medium for log analysis is generally preferable to batch processing in view of the almost inevitable uncertainties regarding key petrophysical parameters and even the compositional nature of subsurface units. KOALA is an interactive package of log analysis routines developed by the Kansas Geological Survey and run on its minicomputer system. Resolution of mineralogic and porosity proportions is made by either maximum variance, unique solution, or least-squares matrix algorithms, depending on the degree of determinancy prescribed by the number of components as related to number of logs. An alternative linear programming method is also available for the incorporation of local geologic information to aid in solutions with restricted log data. Reservoi analyses of fluid saturations, permeability indices, and invasion characteristics are programmed following standard solution procedures. Wherever possible, error diagnostics are generated to alert the user to inconsistencies which are implied between the solutions, input parameters, and log values. Intelligent response to these diagnostics allows the user to initiate revisions in a learning sequence of modifications that converge on a satisfactory solution. Dipmeter data are processed via a variety of graphic options such as flat and perspective cylindrical projections, Wulff and Schmidt polar plots, together with eigenvector analyses of vector fabrics. A simple synthetic seismic modeling procedure is also included and multi-variate statistical procedures, such as discriminant functions and factor analysis, will be incorporated to serve as aids in pattern recognition studies. End_of_Article - Last_Page 441------------

Small Scale Field Test Demonstrating CO 2 Sequestration In Arbuckle Saline Aquifer And By CO 2 -Eor At Wellington Field, Sumner County, Kansas

FREQUENCY CODES AND DUE DATES: A Within 5 calendar days after events or as specified. FGFinal; 90 calendar days after the project period ends. FCFinal; End of Effort. Y Yearly; 90 calendar days after the end of the reporting period. S Semiannually; within 30 calendar days after end of project year and project half-year. Q Quarterly; within 30 days after end of the reporting period. Y180 – Yearly; 180 days after the end of the recipient’s fiscal year O Other; See instructions for further details.

Application of Markov Mean First-Passage Time Statistics to Sedimentary Successions: A Pennsylvanian Case-Study from the Illinois Basin

Markov chains have been widely used in the statistical analysis of sedimentary successions for the discrimination of non-random transitions between lithologies and the examination of potential cyclic patterns. A lithologic transition probability matrix can also be transformed to a matrix of mean first-passage times that represent the expected number of steps for first occurrences between lithologies or facies. These passage times capture the statistics of multiple transition paths and provide a metric of distances that can be used for comparisons between sections separated stratigraphically or geographically. In addition, systematic long-term elements can be differentiated from the short-term model provided by the limited memory contained within a transition probability matrix. A case-study example is described that demonstrates the use of mean first-passage times to show changes in the interplay of deltaic and marine facies, based on transition matrices from type sections of Pennsylvanian formations in the Illinois Basin.