HERSCHER GALESVILLE STORAGE EXPANSION PROJECT

A Review of the steps taken to expand the working capacity of one of the oldest natural gas storage aquifers in the world.

Herscher was developed in 1953 and has been an important storage field in the Natural Gas Pipeline Company of America (NGPL) system since that time. Herscher is designed to provide peak winter supplies of natural gas to the Chicago market.

Frederick W. Metzger Vice President Gas Storage Engineering

Kinder Morgan Energy Partners

Daniel Gillespie Sr. Reservoir Engineer

Kinder Morgan Energy Partners

Natural Gas Pipeline Company of America (NGPL) is in the process of drilling 30 new wells at the Herscher Storage Field located in Kankakee County, Illinois to provide an additional 10.0 Bcf of customers cycled working gas capacity in the Galesville formation. NGPL will offer this additional working gas volume as Nominated Storage Service (NSS), which is a firm storage service that is currently sold out and in high demand. The Herscher Galesville storage field located approximately sixty-five miles from the Greater Chicago Market at the north end of NGPLs system and about 40 miles south of the termini of NGPLs Amarillo and Gulf Coast main lines.

The Herscher Galesville Storage Field is an aquifer located near the town of Herscher, Illinois. Initial injection began in 1953 into the Galesville sandstone storage reservoir. The present total inventory is 37.5 Bcf with a peak day withdrawal rate of 1,000 MMcf/d. The Herscher Galesville gas storage reservoir is located on the Herscher Anticline in southwestern Kankakee County, Illinois. It is a doubly, plunging anticline, approximately, 7-1/2 miles in length and 3-1/2 miles in width trending NNW - SSE. The Galesville formation occurs at an average depth to top of structure of 1,750 feet. It is approximately 100 feet thick with an average porosity of 19 to 20% and an average permeability of 450 to 500 md. At the top of the Galesville at Herscher is a fine to medium grained, friable to unconsolidated, generally well-sorted, clean, massive sandstone containing thin, wavy, clay-shale laminations and interbedded with hard, dolomitic sandstone. The anticlinal structure of the Galesville formation has adequate closure and control to expand the reservoir by 12.0 Bcf of which 2.0 Bcf is required as additional cushion gas. Currently, the reservoir contains 37.5 Bcf of full inventory with 13.35 Bcf of working gas and 24.15 Bcf of cushion gas. This project will allow for the expansion of the working gas capacity by 10.0 Bcf from 13.35 to 23.35 Bcf. After the expansion, the total actual inventory will be 49.5 Bcf.

The primary reservoir constraint affecting this expansion is the influx of water from the outlying areas of the Galesville formation during injection which limits the seasonal injection rate. The storage reservoir is operated continuously at pressures below the original water pressure by water removal during the gas injection season both below and outside the gas bubble in the Galesville formation. The water removal allows the gas to be injected at a sufficient rate to return the working gas volume during the injection season. To expand the working gas volume, additional water must be removed annually from the reservoir to increase the area in which gas can be injected (which in turn allows for an average gas injection rate) and to return the larger working gas volume. The produced water is then disposed into the Prairie Du Chien and the Trempealeau formations which are above the Ironton caprock formation. NGPL has Illinois Department of Natural Resources

authorization to dispose water into these formations. Disposal of water above the Ironton has proven effective to maintain a hydraulic seal on the Ironton caprock for reservoir gas containment. Current operations involve the use of twenty water withdrawal wells in the Galesville formation and twenty-seven water re-injection wells completed in the Prairie Du Chien and the Trempealeau formations.

The primary approach to expanding the working gas volume in the Herscher Galesville is to increase the amount and rate of water removal from the Galesville formation. Fifteen new water withdrawal wells are proposed to be drilled down dip of the existing Galesville gas bubble. The new wells will be equipped with 230 horsepower downhole submersible pumps, each capable of withdrawing up to 20,000 barrels of water per day. The number and location of wells selected for drilling were based on reservoir simulation studies to predict gas bubble growth from water removal by optimizing well spacing and reservoir performance. History matches were developed utilizing gas injection and withdrawal data, water production, bottom hole and surface pressure readings from key field observation wells and field operation practices. Simulation runs were generated for various expansion cases and were used to determine pump well quantity and placement, gas bubble growth and behavior.

The increase in water removal will require additional water disposal capacity. NGPL proposes to obtain this additional capacity by: 1) installing twelve new water lines at various locations within the existing system to tie in new wells and loop or replace existing smaller lines to eliminate flow restrictions and optimize the overall flow direction for the water to be re-injected; 2) installing three 400 horsepower surface booster pumps and associated surface tanks at three existing water re-injection wells; 3) re-entering up to four existing disposal wells and drilling open hole horizontal laterals through the Prairie du Chien and Trempealeau formations; and 4) drilling from seven up to eleven new associated water re-injection (disposal) wells. The new disposal wells will be drilled as twin wells to the surface locations of new pump wells whenever possible to minimize infrastructure costs and disturbed ground area. In addition, NGPL anticipates that positive results from the horizontal lateral recompletions will reduce the number of new disposal wells required on a one for one basis (i.e. one less new water injection well for each successful recompletion), further minimizing disturbed ground area.

This expansion project will require an increase in late season deliverability over existing deliverability to support the new NSS service. In order to meet this increased demand of approximately 100 MMcf/d, NGPL proposes to re-enter five existing Galesville gas injection/withdrawal wells and underream and deepen the existing open hole interval in the Galesville formation in an underbalanced environment. The underreaming procedure will increase the wellbore diameter from approximately seven to fourteen inches over the length of the existing openhole interval (14 to 20 feet) and each well will also be deepened up to five feet, staying above the gas/water interface. This technique to stimulate and improve a wells deliverability is based on successful results with similar workovers on wells in this field in the past.

The proposed Herscher Galesville expansion has been designed to result in minimal impact on the environment. The majority of the up to twenty-six new wells will be located at existing well sites or along existing pipeline right-of-way, and will be directionally drilled to their desired bottomhole locations. Only eleven surface drilling sites will be required for all of the new wells. Seven of the drilling pad sites will be located at existing sites. All of the proposed horizontal recompletions, workovers and booster pump locations are on existing sites as well and, therefore, no newly disturbed ground is required. Directional drilling of the new wells from existing well sites will significantly reduce the surface area requirements for drilling locations and will also include areas previously disturbed by drilling or pipeline operations. Most of the new wells will require only a short run of pipe to connect them to the existing water disposal system. Having multi-well surface pads will also enhance operating efficiency and operator safety. An additional benefit from directional drilling is that the slightly higher cost of the new wells will be more than offset by the avoided construction of longer laterals had vertical wellbores been drilled at each bottom hole location.

The well design and construction will also help increase water removal and re-injection in the new wells. Both the water removal and disposal wells will be directionally drilled and the disposal wells will be completed horizontally in the formations of interest to allow greater exposure to the reservoirs rock face. These two factors will increase the wells ability to remove Galesville formation water and inject it elsewhere.

To accomplish the contemplated increase in working gas volume and the associated increase in the withdrawal rate from Herscher Galesville, it is necessary to increase the available compressor horsepower (hp) on the Herscher Galesville system at NGPLs Compressor Station. The Herscher Galesville system currently has 41,000 hp for gas compression consisting of nine units. As part of the expansion, an additional 8,180 hp unit will be installed.