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A massive Cook Inlet gas resource Consultant says there may be 1,300 trillion cubic feet of natural gas dissolved in non-potable water aquifers that could be produced Alan Bailey Petroleum News
There are massive quantities of methane, the primary component of natural gas, dissolved in non-potable aquifers in the Cook Inlet region, Gary Player, a consulting petroleum geologist, told the American Association of Petroleum Geologists Pacific Section annual meeting on May 22 in Anchorage. Methane is found naturally dissolved in groundwater in gas bearing regions. And it should be feasible to produce the gas from the water, thus opening up an almost limitless supply for local use or for export, Player said. Player has estimated that there may be as much as 1,300 trillion cubic feet of gas stored in this way in the Cook Inlet basin.
Player bases his confidence on a track record of gas production from water in Japan and on his own tests into the use of the technique.
“They’ve done it in Japan for years but haven’t done in much in the states,” Player said.
Test production Player said that he had conducted a test using a well in California. After pumping some water from the well, methane bubbled from the water. He said that in 2010 he tried conducting a deep test in the Gulf Ranch gas field in California. And in 2013 he conducted another test, pumping water for 24 hours from another California well and found a concentration of almost 17 cubic feet of methane per barrel of water from the well. This concentration of gas matched predictions from research conducted at San Diego State University into the solubility of methane in water, Player said.
The water came from a flat aquifer directly above a gas field. In general, water from an aquifer like this can be produced quite easily, sometimes using natural artesian pressure, Player said.
Cook Inlet basin In the Cook Inlet basin, Player has used mapped thicknesses of rocks in the Kenai group to estimate the potential volumes of gas dissolved in water in the basin, factoring in the percentage of potential water-carrying sands in the group and the need for the water bearing rocks to be at some minimum depth. He estimated the existence of some 52 trillion barrels of water. Based on the potential volume of gas in the water, he estimated the possibility of 1,300 trillion to 1,450 trillion cubic feet of gas dissolved in the water, depending on which version of a basin map he used.
Looking at various parts of the basin, he estimated there to be 667 tcf in the northern half of the Kenai Peninsula, 236 tcf in the southern Kenai Peninsula and 89 tcf in the northwestern sector of the basin. So there may be something in the order of 1,000 tcf of dissolved gas just in the onshore portion of the basin, Player suggested.
And the wells required to develop this resource would only need to be 4,000 to 5,000 feet deep, he said.
Production technique The concept of gas production from water would involve extracting water from a saline aquifer containing dissolved gas, not from a potable aquifer. In a separator at the surface the gas would effervesce from the water and be directed through a production system. The used water would then be pumped back into the aquifer, both for disposal and for aquifer pressure maintenance.
In the Cook Inlet basin, the drilling of 500 dissolved gas wells, each perhaps making 400 mcf (thousand cubic feet) per day of gas could a result in total production of 200,000 mcf per day, perhaps for 30 or 40 years. The potential longevity of the production is based the technique’s Japanese track record, Player said. With the total cost of the wells perhaps being $400 million, the economics of this venture would appear favorable compared with the massive cost of building a gas pipeline from the North Slope, he suggested.
Conducting a similar analysis in California suggests a resource of as much as 2,000 tcf of gas in that state, Player said.
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