Table of Contents

Vol. 6, No. 4
4th Quarter 2000

Reservoir Characterization for the Next Millennium

February 1, 2000 (Midland, Tex.) by Texas Region

BOTTOM LINE

Advanced technologies including computer visualization, multi-component seismic, fracture modeling, and borehole imaging are being developed by the Bureau of Economic Geology, The University of Texas at Austin. Opportunities exist for operators to participate with the Bureau in characterization and reservoir exploitation studies to increase oil and gas recovery on State and University Lands.

PROBLEM ADDRESSED

Advanced technologies with great promise for reservoir characterization studies are being developed at the Bureau of Economic Geology, The University of Texas at Austin. Advanced visualization, especially virtual imaging, has already begun to redefine approaches to characterization and field management. A new multi-component seismic technique, currently being developed, will provide better understanding of stratigraphic relationships, lithological distributions, and pore-fluid properties. Quartz-filled microfractures in clastic sediments from fractured reservoirs are being utilized to quantify the size distributions of much less abundant macrofractures that can control fluid flow. This technique is proving to be a cost-effective way to construct a dual-porosity simulation for large regions in the subsurface. Borehole imaging logs, when properly calibrated with core, can resolve facies successions and some karst features with degrees of accuracy that can rival core description.

Controlling Sand Production

Nov. 18 & 19, 1999 (Long Beach & Bakersfield, Calif.) by West Coast Region

BOTTOM LINE

Cost-effective solutions exist for controlling sand production, ranging from conventional gravel packs to High Rate Water Packs to Frac Packs to a novel steam sand consolidation completion technique. But operators must know when to apply the different solutions. Controlling proppant flowback after fracturing is also critical.

PROBLEM ADDRESSED

In certain areas (like much of California), sand production is a major operational problem. In some circumstances, it is most economical for operators to just live with the problem. Even then operators must deal with erosion problems, as well as sand fill whenever production is interrupted, and eventual wellbore collapse. Frequently though, sand control treatments are required. Like with most problems, there are several technology options-open hole or cased, conventional gravel pack, prepacked screens or liners, Frac Packs or High Water Rate Sand Packs, etc. This workshop provides a comprehensive look at sand control and the knowledge required to choose the optimum solution.

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Surface Exploration Methods in Mature Basins

December 10, 1999 (Lansing, Mich.) by Midwest Region

BOTTOM LINE

Surface exploration for hydrocarbons can be optimized by meeting three conditions: (1) more than one well-designed method is used during an interdisciplinary effort, (2) the results are integrated with subsurface geological and geophysical reality, and (3) calibration surveys are run for known reservoirs or recent discoveries. By doing so, operators can cost effectively reduce exploration and development risks.

PROBLEM ADDRESSED

Producers are continually looking for cost-effective approaches to reduce exploration and development risks-from pursuing leads and prospects to high-grading leases to assessing reservoir compartmentalization. When combined with subsurface geological and geophysical information, surface exploration methods can reduce risk. Importantly, they can verify the presence of hydrocarbons. Surface expression of hydrocarbon seepage takes many forms, which has led to the development of many surface exploration methods. The most successful methods are based on direct detection of hydrocarbons or hydrocarbon-induced alteration anomalies.

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Exploring Appalachia's Middle Ordovician Carbonates

November 11, 1999 (Morgantown, W. Va.) by Appalachian Region

BOTTOM LINE

A primary key to commercial production from the carbonates of the Ordovician Trenton-Black River Group is the presence of fractures associated with basement faults that served as conduits for dolomitizing fluids. These fractures enhanced matrix permeability and now serve as permeability pathways.

PROBLEM ADDRESSED

The areal extent of the Ordovician Trenton-Black River Group in the Appalachian Basin is large. Acquiring and communicating to regional producers a working knowledge of the conditions under which success has already been achieved could substantially enhance commercial production.

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Horizontal Drilling in Oil Shales

January 26, 2000 (Jackson, Miss.) by Eastern Gulf Region

BOTTOM LINE

Improvements in horizontal drilling of fractured oil shale plays can have a steep learning curve. Attaining a cost-effective level of success can be related to efficiency of drilling, proper orientation of the horizontal leg to intersect the maximum number of fractures, avoiding formation damage, using appropriate mud systems, and avoiding early drawdown that will close fractures and cut off hydrocarbon drainage into the wellbore. Future success in drilling horizontal wells in the Tuscaloosa Marine Shale of the Gulf Coast may depend on adapting technologies developed in other basins.

PROBLEM ADDRESSED

A single successful horizontal well in the Tuscaloosa Marine Shale indicates that lessons and technologies must be transferred from other oil shale plays. Orientation of fractures controlling fluid flow should be determined to ensure proper orientation of the horizontal leg. Drilling slightly underbalanced and using oil-based muds in oil-wet reservoirs may help to prevent formation damage. Unlike vertical wells, horizontal wells cannot be stimulated by sand proppant. Adequate circulation must be ensured to keep the wellbore clean, otherwise tool sticking is likely. DSTs and IP tests may cause sufficient drawdown to close microfractures adjacent to the wellbore. Exploration strategies include mapping areas of thick black shale, peak hydrocarbon generation, fracture intensity, and drilling near good wells. Specialized maps such as 2nd derivative maps to indicate zones of high fracture intensity may be very useful.

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CO2 Flooding Potential-Morrow in Western Kansas & Oklahoma Panhandle

November 17, 1999 (Wichita, Kans.) by North Midcontinent Region

BOTTOM LINE

Miscible CO₂ flooding is a feasible option to help increase oil production from Morrowan reservoirs in western Kansas and Panhandle Oklahoma. There is a significant recovery potential for properly applied projects at a current threshold level of about $15-20/barrel oil.

PROBLEM ADDRESSED

Miscible CO₂ flooding has proven to be a viable EOR recovery process when conscientiously applied to Morrowan reservoirs. However, because of Morrow reservoir heterogeneity, detailed CO₂ feasibility and flood design studies should be performed to help determine if a reservoir is a good candidate. Studies from analogous reservoirs should also be consulted. Key sensitivities for Morrow CO₂ flooding include oil price and amount of incremental oil production. The total investment for developing a typical Morrow CO₂ unit (26 million barrels OOIP, 1.3 million barrel recoverable from CO₂ flooding) is estimated at about $2.63 million. Based on current economics and field results from Postle Unit, it is estimated that CO₂ floods in Morrow reservoirs have potential for an additional 50 to 75 million barrels oil.