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===Formation collapse===
===Formation collapse===
In loosely consolidated or weakly cemented formations, the severe pressure drop that occurs around a wellbore can cause the formation to collapse. When this occurs, the pore structure is altered and the permeability is reduced, causing skin damage around the wellbore. To prevent this, a small hydraulic fracture treatment can be performed early in the life of the well. The fracture treatment will help minimize the pressure gradients and reduce the chance of formation collapse around the wellbore.
In loosely consolidated or weakly cemented formations, the severe pressure drop that occurs around a wellbore can cause the formation to collapse. When this occurs, the pore structure is altered and the permeability is reduced, causing skin damage around the wellbore. To prevent this, a small hydraulic [[fracture]] treatment can be performed early in the life of the well. The fracture treatment will help minimize the pressure gradients and reduce the chance of formation collapse around the wellbore.
As the pressure is depleted throughout the reservoir, the overburden pressure caused by the overlying rock tends to compress the formation. This overburden pressure can also alter the pore structure and reduce the permeability. The degree of severity is a function of the formation compressibility. Soft formations, such as those found in the Gulf Coast, can experience reductions in permeability by a factor of 10 or greater. More competent sandstones or carbonate reservoirs may only experience a small reduction in permeability. These effects must be taken into account when predicting long-term performance; otherwise, predictions will be too optimistic.
As the pressure is depleted throughout the reservoir, the overburden pressure caused by the overlying rock tends to compress the formation. This overburden pressure can also alter the pore structure and reduce the permeability. The degree of severity is a function of the formation compressibility. Soft formations, such as those found in the Gulf Coast, can experience reductions in permeability by a factor of 10 or greater. More competent sandstones or carbonate reservoirs may only experience a small reduction in permeability. These effects must be taken into account when predicting long-term performance; otherwise, predictions will be too optimistic.