Abstract:

Mudstone is a kind of clastic rock, which possesses pores and porosity, there is also permeability, but its permeability is quite poor due to the extremely small openness of pores. Mudstone can definitely transport water with poor permeability. Oil wells usually produce a little quantity of water at beginning of production, which comes from the mudstones lying over and under the reservoirs, not the formation water dissolved in crude oil. The abnormal pressure in formations is resulted from the geological accidents, and is a temporary status of pressure, which is so far not balanced by water transportation in mudstones during short time.

Key words: formation, mudstone, pressure, water cut, abnormal pressure