Research and Field Application of Carbon Dioxide Composite Fracturing Fluid

There are many problems of carbon dioxide dry fracturing now, such as sealing equipment, high cost, low sand concentration, small fracturing and high treatment difficulty. The carbon dioxide composite fracturing fluid is researched, based on conventional equipment and 70% carbon dioxide on the normal pressure conditions. The thickening of liquid carbon dioxide and the method of water-based continuous viscosity are studied, based on the carbon dioxide visual sample. The interaction of two liquid thickeners (water based and carbon dioxide based) was studied. And the influences of water proportion and temperature on the carbon dioxide based composite thickening performance are also studied. It is studied that 2% carbon-dioxide based thickener and 2% water-based thickener can effectively thicken liquid carbon-dioxide and water. In addition, the compatibility of the two thickeners is perfect. When the proportion of carbon-dioxide water-base composite fracturing fluid is less than 30%, and the temperature is above 5℃, the performance of suspending proppant is excellent. The technology has been tested in 2 wells. The cumulative volume of water-based fracturing fluid in NPXX well is 267 m3, liquid carbon dioxide is 910 m3, the highest sand ratio reaches 35%, and the cumulative proppant addition is 46.5 m3. Prominent increasing production has been achieved.