Scholarly record

CHARACTERISATION OF ARISING LOW MINERALIZED WATER IN A DEEP OIL/GAS FIELD WELL IN RISHA/JORDAN BY CHLORINE-36 AND HYDROCHEMICAL METHODS AND ITS POSSIBLE CONSEQUENCES FOR FURTHER PRODUCTION

W. Balderer, H. A. Synal, F. Leuenberger

Abstract

Within the Risha well field in Eastern Jordan oil and especially gas is produced from the existing traps on the top of the Ordovizium deposits, at a depth of about 2000 m. By more than 30 deep wells oil and gas is produced which contains also a portion of water. Usually this water accompanying the oil production is highly mineralized and originates, according to chemical and stable isotope analyses, most probably from old syn- sedimentary brines or formation water. Usually this water accompanying the oil production is highly mineralized and originates, according to prior chemical and stable isotope analyses, most probably from old syn- sedimentary brines or formation water. The initiating impulse for the present study using the 36Cl isotope method was the appearance of weakly mineralized water in a newly drilled borehole. This borehole was not producing oil and gas in a similar, industrial useable amount as in the preceding boreholes. The application of the 36Cl isotope technique, a radioisotope with a half life of 301’000 years was used to help tackle the economically important question of the origin of this unexpected occurrence of low mineralized water: Is it i) due to an admixture of drilling fluid within one individual borehole or ii) due to the influx of a moderately mineralized deep seated groundwater of a regional aquifer or iii) due to induced infiltration along fault zones and successive mixing with deep formation fluid. If this induced flow caused by an adjacent fault zone really exists this would indicate that the gas reservoir is dependent on the preservation of the hydraulic head of the water filled fault system, in order to prevent any leakage out of the deep reservoir.

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