Influence of hysteretic stress path behavior on seal integrity during gas storage operation in a depleted reservoir

In this study,we numerically investigate the influence of hysteretic stress path behavior on the seal integrity during underground gas storage operations in a depleted reservoir.Our study area is the Honor Rancho Underground Storage Facility in Los Angeles County(California,USA),which was converted into an underground gas storage facility in 1975 after 20 years of oil and gas production.In our simulations,the geomechanical behavior of the sand reservoir is modeled using two models:(1)a linear elastic model(non-hysteretic stress path)that does not take into consideration irreversible deformation,and(2)a plastic cap mechanical model which considers changes in rock elastic properties due to irreversible deformations caused by plastic reservoir compaction(hysteretic stress path).It shows that the irreversible compaction of the geological layer over geologic time and during the reservoir depletion can have important consequences on stress tensor orientation and magnitude.Ignoring depletion-induced irreversible compaction can lead to an over-estimation of the calculation of the maximum working reservoir pressure.Moreover,this irreversible compaction may bring the nearby faults closer to reactivation.However,regardless of the two models applied,the geomechanical analysis shows that for the estimated stress conditions applied in this study,the Honor Rancho Underground Storage Facility is being safely operated at pressures much below what would be required to compromise the seal integrity.

Migration of total chromium and chloride anion in the Rocha River used for estimating degradation of agricultural soil quality at the Thiu Rancho zone

The Rocha River is a receptor to receive wastewater from household,hospital and industry,from where contaminants are transported in the river,affecting biodiversity and the ecosystem of the area.In this paper we estimated the maximum transport of total chromium and chloride anion by applying the analytical model of Ogata&Banks(1961),and the results obtained are grouped into three zones:Contaminated,transition,and uncontaminated.The analytical model was applied with 13 samples collected from the river piezometers installed near Rocha,where they are arranged in two lines,i.e.RH-1 to RH-6 as the first line and RH-9 to RH-12 as the second line.The total chromium concentrations range from 0.16 mg/L(RH-1)and 0.11 mg/L(RH-9)at the closest points to Rocha River,to 0.13 mg/L(RH-7)and 0.03 mg/L(RH-12)at the most remote points to the river.The advance of the pollutants does not exceed 50 meters with respect to the axis of the Rocha River.