Salinity Effects On Water Thickeners For Enhanced Oil Recovery
Authors: Norton Charles J. , Falk David O. 
Published: December 2007

Acceptable disposal of saline production waters poses a serious environmental and economic problem poses a serious environmental and economic problem in oil recovery. An attractive solution to this problem would be to reinject these waters in tertiary problem would be to reinject these waters in tertiary recovery operations. The effects of fresh (soft) and produced (hard) waters of formulation and displacement produced (hard) waters of formulation and displacement (scavenger or drive water) on six potential water thickeners for the Maraflood oil recovery process are reported. The thickeners studied are Dow 700 partially hydrolyzed polyarcylamide (PHPA), Marathon partially hydrolyzed polyacrylamide (DRC P PHPA), Polyox, carboxymethycllulose (CMC), Kelco PHPA), Polyox, carboxymethycllulose (CMC), Kelco and Midwest Solvents xanthan gum broths, and Kelzan mf dried xanthan biopolymer flooded in Berea sandstone at 1 ft/day and in Henry formation cores at 0.28 ft/day mean rates. Artificial soft water (Palestine water, PW) and an artificial hard water (Henry Plant water, HPW) were studied for their oil recovery effects as waters of formulation and displacement with the various water thickeners used to displace a 0.04 PV of 119-R sulfonate slug under tertiary flooding base-case conditions (see footnote on Table 1 for details).

In general, hard water has an adverse effect as a water of formulation; but hard water can be used with little or slight loss in oil recovery as displacement water. In several cases, an actual oil recovery improvement is obtained on formulating up to 50 percent of the second polymer solution (0.6 PV) with hard water in the base-case flood sequence. These approaches permit the disposal of much of the hard production water.

In Berea cores with the Dow 700 PHPA oil recoveries of about 82 percent are obtained for concentrations of 210 to 500 ppm in soft water. HPW can be used for displacement, but there is some loss in oil recoveries on going to more saline waters for formulation. Oil recoveries at 500-ppm average formulation diminish in the order PW-HPW PW-PW HPW-PW HPW-PW, where the particular water of the first 0.1-PV formulation and the second 0.6-PV formulation are indicated by the abbreviations.

DRC PHPA is comparable to Dow 700, giving oil recoveries in the range of 75 to 83 percent for concentrations of 210 to 500 ppm in soft water. Oil recoveries improve with some HPW in the formulations, but there is significant loss in going to hard water for complete formulation. The oil recovery order at 500 ppm is PW-HPW greater than PW-PW greater than HPW-PW greater than HPW-HPW.

Polyox gives oil recoveries in the range of 45 to 48 percent obtained at 210-to 500-ppm thickener in soft water. The oil recovery order at 500-ppm is PW-PW HPW-PW greater than PW-HPW greater than PW-PW HPW-PW greater than PW-HPW greater than HPW-HPW.

The thickener carboxymethycellulose (CMC 7H3S) gives oil recoveries in the range of 62 to 63 percent at concentrations of 210 to 500 ppm in soft water and holds promise for further improvement for economic thickeners for oil recovery. The oil recovery order at 500 ppm is PW-PW PW-HPW greater than HPW-PW greater than HPW-HPW.

Kelco xanthan broth gives oil recoveries in the range of 50 to 66 percent for concentrations of 210 to 500 ppm in soft water. Surprisingly better oil recoveries are obtained with the PW-HPW and HPW-PW systems. The oil recovery order at 500 ppm is PH-HPW HPW-PW PW-PW HPW-HPW. Kelco broth, in PH-HPW HPW-PW PW-PW HPW-HPW. Kelco broth, in general, gives better oil recoveries and less adverse salinity effects than dried Kelzan mf.

The dried xanthan biopolymer Kelzan mf gives oil recoveries in the range of 47 to 70 percent at 210 to 500 ppm in soft water. The order at 500 ppm of the oil recovery is PW-PW greater than HPW-PW greater than HPW-HPW.

A Midwest Solvents xanthan broth gave oil recoveries in the range of 63 to 81 percent at 210 to 500 ppm in soft water-better recoveries than obtained with Kelco broth or Kelzan mf.

Introduction

Acceptable disposal of saline production waters poses a serious environmental and economic problem in poses a serious environmental and economic problem in oil recovery. An attractive solution to this problem would be to inject these waters in tertiary recovery operations.