Abstract:

The existance of effective caprocks is one of the important factors for the formation of gas pools. The confining capacity is relative, which might constitute effective sealing for some pools but might be ineffective or low-effective for others under the same confining condition. The gas-bearing height of a pool could be calculated quantitatively by use of the difference between the breakdown pressrure in cap rocks and displacement pressure in reservoir. But that gas in traps could accumulate to form pools or not is decided by thedifference between confining force and total force including buoyant force, hydrodynamic force, residual pressure, the difference between the supplemental force and escaping force of the gas and the damage degree of tectonic movement in late stage. It is only by applying the view of dynamic balance, can we make a correct assessment on natural gas preservation condition.