Analysis and Treatments of Heglig Oilfield Produced water for Reuse in Water Base Fracturing Fluids

Abstract

Produced water is the water produced with oil or gas during well production as a result of different operations. Recently, many Sudanese oil fields suffer from the massive amount of water production; the most water production problems in Sudan was observed in Heglig oilfield. The Heglig oilfield is located in Muglad Basin in the southeast and middle of Block 2 in Sudan. The oil production from Heglig oilfield was reported to have peaked in 2006, however it has been declined now and the water cut was reached 95%. Due to many environmental impacts, several studies were conducted for treating the produced water from Heglig oilfield to be used in irrigation; no work was presented to study the possibility of reusing the produced water in oil operations in the fields. However, this work analyzes and treats the produced water from Heglig oilfield and evaluates the possibility of the treated water for the re-using in water base fracturing fluids. Samples were collected from two different ponds in the field and analysed according to the American Public Health Association (APHA) and the result were compared with (National Recommended Water Quality (EPA)) to identify the required treatments for the collected water.

Two different samples of Natural zeolite (Zn1 and Zn2) were used to absorb the different metals from the collected water under different conditions of pH and zeolite concentration. Also, the effect of the different metals in the rheological properties of water base fracturing fluids was addressed under different pH, temperature and shear rate for two types of fluid using Hydroxyethyl Cellulose (HEC) and Carboxymethyl Hydroxyethyl Cellulose (CMHEC) as gelling agents and Borate as cross-linking system.

The result presented that natural zeolites hold great potential to decrease the cationic, heavy metals and the adsorption capacity depends on the pH; better adsorption was achieved with 0.5 g of Zn2 at pH of 1 while deposition of yellow color insoluble solid has been observed with Zn1 under different concentrations. The cross-linking ability of the fracturing fluid presented that better cross-linking system were achieved with 0.48g CMHEC at pH of 8 and temperature of 40 ˚C for HEC and 60 ˚C CMHEC; while effect of metals concentration can be neglected on HEC crosslinking behaviour. Key Word: Produced water; Natural Zeolite; Fracturing Fluid; cross-linking system