Abstract
As a well ages, the reservoir pressure decreases and the liquid starts to accumulate at the bottom hole. Without reducing the hydrostatic head via deliquification technology, production would more rapidly decrease than the natural decline curve and would cease completely. In gas fields, foamers are very attractive deliquification technology as they are relatively economic and flexible technology. Conventional water-based foamers have been very successful for deliquifying wells to enhance gas production and reducing hydrostatic pressure. However, there has been very little success in treating oil-loaded wells with foamer due to the difficulties in foaming crude oil.
Novel chemistry that foams crude oil was identified, and a new oil foamer was developed as a solution for oil-loaded wells. This oil foamer was tested in wide range of crude oils and water cuts to determine the type of liquid that the new oil foamer treats cost effectively. Lab tests showed that the new oil foamer effectively treated liquid with an API gravity range of 25~40 and a water cut up to 60 percent.
A field trial at an EOG well in South Texas proved that the new oil foamer increased gas and oil production. Historically, this well produced intermittently due to low reservoir pressure. The average production prior to the field trial was 40 BOPD and 250 Mcf/D when the well produced. Average oil and gas production for the 60-day period prior to oil foamer injection was only 13 BOPD and 122 Mcf/D.
Lab tests determined the recommended dosage of the oil foamer and defoamer, and the dosage was optimized during the field trial. The oil foamer was applied continuously through a capillary at a rate of 750 ppm after optimization. The defoamer was injected at the wellhead to control the foam issue at the surface equipment. The oil foamer application increased production from 7 days to 12 days. Gas production increased from 122 Mcf/D to 400 Mcf/D, and oil production increased from 13 BOPD to 100 BOPD. During the entire field trial, the defoamer successfully controlled the foam issue, and the foam did not pose any upset to surface equipment.
