Geochemical Characteristics and Distribution of Associated Resources in Ordovician Oilfields of Tahe Oilfield, Tarim Basin

The water resources of the Ordovician oilfield in the Tarim Basin's Tahe Oilfield are characterized by a high concentration of potassium, lithium, and other trace elements with significant economic value. These resources represent an important strategic asset in the Tarim Basin, alongside oil and gas resources. In this paper, Ordovician oilfield water samples from the Tahe oilfield were collected and analyzed to study its geochemical characteristics and its associated resource distribution pattern. The results demonstrate that the primary cations present in the Ordovician oilfield water of the Tahe Oilfield are Na⁺, Ca²⁺, K⁺, and Mg²⁺, while the primary anions are Cl⁻, SO₄²⁻, HCO³⁻, and NO₃⁻. The mineralization of the oilfield water ranges from 140 to 260 g/L, with an average value of 216.56 g/L, indicating a medium level of mineralization. The oilfield water can be classified as a CaCl₂ type. The characteristic coefficients indicate that the oilfield water undergoes alternating cation adsorption and robust water-rock interactions. It is a solution-filtered oilfield water, exhibiting complete reduction, optimal reservoir confinement, and a notable degree of metamorphism. The ions present in the oilfield water are predominantly derived from rock salt, gypsum, and crumbly clay minerals. The useful components, including K⁺, Li⁺, Br⁻, and Sr²⁺, exist in oilfield water can meet the industrial indicators of comprehensive utilization: the K⁺ content ranging from 556 to 2740 mg/L with an average value of 1781.19 mg/L; the Li⁺ content varying from 2.9 to 18.5 mg/L with an average concentration of 11.16 mg/L; the concentration of Br⁻ ranging from 45 to 323 mg/L with an average concentration of 230.77 mg/L; The concentration of Sr²⁺ ranging from 341 to 605 mg/L with an average of 473.31 mg/L. Conducting research on oilfield water that coexists with oil and gas resources, and comprehensively developing and utilizing the associated resources, is of significant importance for enhancing the resource value of oil and gas fields.