Willard J. Guy

Characterization of the Mississippian chat in south-central Kansas

To understand production from low resistivity-high porosity Mississippian chat reservoirs in south-central Kansas it is necessary to understand the nature of deposition and diagenesis, how tectonics is a factor, the lithofacies controls on petrophysical properties, and log response to these properties. The initial mudstones to sponge-spicule wacke-packstones were deposited in transgressive-regressive (T-R) cycles on a shelf to shelf margin setting, resulting in a series of shallowing-upward cycles. Sponge-spicule content appears to increase upward with increasing cycle thickness. After early silicification, inter- and post-Mississippian subaerial exposure resulted in further diagenesis, including sponge-spicule dissolution, vuggy porosity development in moldic-rich rocks, and autobrecciation. Meteoric water infiltration is limited in depth below the exposure surface and in distance downdip into unaltered, cherty Cowley Formation facies. Areas of thicker preserved chat and increased diagenesis can be correlated with structural lineaments and, in some areas, with recurrent basement block movement. Combination of folding or block fault movement prior to or during development of the basal Pennsylvanian unconformity, sponge-spicule concentration, and possibly thickness of overlying bioclastic wacke-grainstones resulted in variable reservoir properties and the creation of pods of production separated by nonproductive cherty dolomite mudstones. These events also resulted in alteration of the depositional cycles to produce a series of lithofacies that exhibit unique petrophysical properties. From bottom to top in a complete cycle seven lithofacies are present: (1) argillaceous dolomite mudstone, (2) argillaceous dolomite mudstone that has chert nodules, (3) clean dolomite mudstone that has nodular chert, (4) nodular to bedded chert, (5) autoclastic chert, (6) autoclastic chert that has clay infill, and (7) bioclastic wacke-grainstone. The uppermost cycle was terminated by another lithofacies, a chert conglomerate of Mississippian and/or Pennsylvanian age. The chert facies exhibit porosities ranging from 25 to 50% and permeabilities greater than 5 md. The (Begin page 86) cherty dolomite mudstones, argillaceous dolomite mudstones, and bioclastic wacke-grainstones exhibit nonreservoir properties. Reservoir production, numerical simulation, and whole core data indicate fracturing can be present in chat reservoirs and can enhance permeability by as much as an order of magnitude. Capillary pressure data indicate the presence of microporosity and can explain high water saturations and low resistivity observed in wire-line logs. Relative permeabilities to oil decrease rapidly for saturations greater than 60% and may be influenced by dual pore systems. Archie cementation exponents increase from 1.8 for mudstones to more than 2.5 in the cherts that have increasing sponge-spicule mold and vug content. Detailed modified Pickett plot analysis of logs reveals critical aspects of chat character and can provide reliable indices of reservoir properties and pay delineation. Models developed provide additional insight into the chat of south-central Kansas and understanding of the nature of controls on shallow-shelf chert reservoir properties.

Field Demonstration of Carbon Dioxide Miscible Flooding in the Lansing-Kansas City Formation, Central Kansas

Progress is reported for the period from January 1, 2002 to March 31, 2002. Technical design and budget for a larger (60-acre, 24.3 ha) CO2 demonstration project are being reviewed by the US DOE for approval. While this review process is being conducted, work is proceeding on well testing to obtain reservoir properties and on the VIP reservoir simulation model to improve model prediction and better understand the controls that certain parameters exert on predicted performance. In addition, evaluation of the economics of commercial application in the surrounding area was performed. In a meeting on January 14, 2002 the possibility of staging the demonstration, starting with a 10-acre sub-pattern flood was raised and the decision made to investigate this plan in detail. The influence of carbon dioxide on oil properties and the influence of binary interaction parameters (BIP) used in the VIP simulator were investigated. VIP calculated swelling factors are in good agreement with published values up to 65% mole-fraction CO2. Swelling factor and saturated liquid density are relatively independent of the BIP over the range of BIPs used (0.08-0.15) up to 65% mole-fraction CO2. Assuming a CO2 EOR recovery rate projected as being most likely by current modeling, commercial scale CO2 flooding at

FIELD DEMONSTRATION OF CARBON DIOXIDE MISCIBLE FLOODING IN THE LANSING-KANSAS CITY FORMATION, CENTRAL KANSAS

20/BO is possible in the leases in Hall-Gurney field. Relatively small floods (240-320 acres, 4-6 patterns) are economically viable at

Geo-Engineering through Internet Informatics (GEMINI)

20/BO in areas of very high primary and secondary productivity (>14 MBO/net acre recovery). Leases with moderately high primary and secondary productivity (> 10 MBO/net acre recovery) can be economic when combined with high productivity leases to form larger floods (>640 acres, 9 or more patterns).

Modeling Petroleum Reservoirs in Pennsylvanian Strata of the MidContinent, USA

Progress is reported for the period from July 1, 2002 to September 30, 2002. On September 27, 2002 the US DOE approved the proposed modified plan to flood a 10+-acre pattern. MV Energy has received informal notification that GE Capital will approve sale of the portion of the Colliver lease involved in the pilot. Murfin Drilling Company is seeking local small independent partners for the pilot and has received commitment from White Eagle Energy and John O. Farmer Oil Company to date. A Contract was signed between the Kansas Department of Commerce & Housing and Murfin formalizing the KSDOC&H contribution of

Log Analysis of Petrofacies and Flow-Units with Microcomputer Spreadsheet Software

88,000 to the pilot project. This money will be used for well rework and testing. The results of this small flood will be used to evaluate the viability of performing a larger-scale demonstration and will be used by the partners to decide their role in a larger-scale demonstration. The 10+-acre pattern requires the least up-front expense to all parties to obtain the data required to accurately assess the viability and economics of CO2 flooding in the L-KC and of a larger-scale demonstration. Proposed modifications to the project plan were reviewed in the previous quarterly technical progress report.

Petrofacies Analysis - A Petrophysical Tool for Geologic/Engineering Reservoir Characterization

GEMINI will resolve reservoir parameters that control well performance; characterize subtle reservoir properties important in understanding and modeling hydrocarbon pore volume and fluid flow; expedite recognition of bypassed, subtle, and complex oil and gas reservoirs at regional and local scale; differentiate commingled reservoirs; build integrated geologic and engineering model based on real-time, iterate solutions to evaluate reservoir management options for improved recovery; provide practical tools to assist the geoscientist, engineer, and petroleum operator in making their tasks more efficient and effective; enable evaluations to be made at different scales, ranging from individual well, through lease, field, to play and region (scalable information infrastructure); and provide training and technology transfer to evaluate capabilities of the client.

From Geomodels to Engineering Models—Opportunities for Spreadsheet Computing

Improved characterization of petroleum reservoirs must include better geologic models in order to predict quantitative attributes of reservoir units. By necessity, petroleum reservoir prediction and modeling must make both interpolations and extrapolations from limited data. Several approaches to modeling of sedimentary rocks include descriptive or conceptual (qualitative) geologic models and geostatistical, simulation (process), and visualization (quantitative) models. Each type of model has its advantages and limitations, including the appropriate scale of application, data requirements, and knowledge as to how the reservoir was formed. All of the models compliment one another, providing views of complex reservoirs from different perspectives. Quantitative modeling potentially can create a more coherent, integrated view of the reservoir than qualitative conceptual models. An optimum model probably includes a combination of approaches based on the extent and type of knowledge about the reservoir.