Changes

==Predicting leakage in deep accumulations==

==Predicting leakage in deep accumulations==

Hydrofractured seal leakage limits the thickness of a petroleum column whether the seal fails during or after charging. Leakage in deeply buried accumulations occurs only where geopressure is close to the fracture gradient (hard geopressures). Hard geopressures are characteristic of shale-dominated basins that have undergone recent rapid subsidence.

Hydrofractured seal leakage limits the thickness of a [[hydrocarbon column|petroleum column]] whether the seal fails during or after charging. Leakage in deeply buried accumulations occurs only where geopressure is close to the fracture gradient (hard geopressures). Hard geopressures are characteristic of shale-dominated basins that have undergone recent rapid subsidence.

We can use downhole fluid pressure analysis techniques (e.g., <ref name=ch11r6>Caillet, G., 1993, The caprock of the Snorre field, Norway: a possible leakage by hydraulic fracturing: Marine and Petroleum Geology, vol. 10, p. 42–50., 10., 1016/0264-8172(93)90098-D</ref> to evaluate hydrofractured seal failure for an area. Leak-off tests estimate the fracture gradient, and mud weight, well logs, or seismic data approximate the fluid pressure gradients. Because gas and condensate have much lower densities than oil, gas columns are more likely to have hydraulic failure than oil columns of the same height in similar settings.

We can use downhole fluid pressure analysis techniques (e.g., <ref name=ch11r6>Caillet, G., 1993, The caprock of the Snorre field, Norway: a possible leakage by hydraulic fracturing: Marine and Petroleum Geology, vol. 10, p. 42–50., 10., 1016/0264-8172(93)90098-D</ref> to evaluate hydrofractured seal failure for an area. [http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=leakoff%20test Leak-off tests] estimate the [http://www.glossary.oilfield.slb.com/en/Terms/f/fracture_gradient.aspx fracture gradient], and [[Pressure prediction: analysis of mud weights|mud weight]], well logs, or [[seismic data]] approximate the fluid pressure gradients. Because [http://www.glossary.oilfield.slb.com/en/Terms/n/natural_gas.aspx gas] and [http://www.glossary.oilfield.slb.com/en/Terms/c/condensate.aspx condensate] have much lower densities than oil, gas columns are more likely to have hydraulic failure than oil columns of the same height in similar settings.

==Predicting leakage in shallow accumulations==

==Predicting leakage in shallow accumulations==