Basin Modeling in the Kuqa Depression of the Tarim Basin (Western China): A Fully Temperature-dependent Model of Overpressure History

摘要

The fully temperature-dependent model of the effective pressure of thensolid matrix and its related overpressure has been derived from the pressure balancenequation, mass conservation, and Darcy’s law, and is directly useful in basin model-ning. Application of the model in the Kuqa Depression of the Tarim Basin in westernnChina proves that this overpressure model is highly accurate. The case of the present-nday values of the calculated overpressure histories of Wells Kela2 and Yinan2 ap-nproach the field-measured data with mean absolute relative residuals of 3% and 5%,nrespectively. This indicates that the overpressure simulation is a practical alternativento using rock mechanics experiments for effective pressure measurement. Since cal-nculation of the overpressure history uses the geohistory model and geothermal historynmodel simulation outcomes, the relevant data used and the output of the two modelsnof the Kela2 well are given as examples.nThe case studies show that the pore fluid density and viscosity used in the calcula-ntion of overpressures should be temperature-dependent, otherwise the calculation re-nsults would deviate far from the field-measured pressure data. They also show that thenmost sensitive parameter governing overpressure is permeability, and permeabilityncan be calculated by using either the Kozeny–Carman formula or the porosity–powernfunction. The Kozeny–Carman formula is better if accurate data for the specific sur-nface area of the solid matrix (Sa) exists, otherwise, the porosity–power function isnused. Furthermore, it is vital for calculating an accurate overpressure history that onencan calibrate Sa in the Kozeny–Carman formula, or index m in the porosity–powernfunction by using field-measured pressure data as a constraint. In these specific casenstudies, the outcome found by using the Kozeny–Carman formula approaches thenoutcome found by using the porosity–power function with m = 4, and both approachnthe field-measured pressure data.