Abnormal Pressure Regimes In Sedimentary Basins And Their Prediction And Detection

Abnormal pressures widely exist in oil and gas basins. Abnormal pressures, especially overpressures directly relate to drilling safety, furtherly relate to personal safety and property loss, and affect the prospecting program of oil and gas. It' s very important for hydrocarbon reservoir finding, casing program design, drilling safety guarantee and hydrocarbon reservoir protection to do abnormal pressure prediction and detection well. On the basis of deeply analysis of causal mechanisms of abnormal pressure and their classification, the generation and distribution of abnormal pressure in Jiyang Depression get be studied, and such overpressure causal mechanisms as aquathermal expansion and tectonic uplift proposed by Li Pilong et al(2004) and underpreesure causal mechanisms are argued against, in the meantime, new causal mechanisms get be proposed. The abnormal pressures effects on elements of hydrocarbon reservoirs and their responses in exploration and drilling instruments are the basis of before and while drilling prediction and detection for overpressures. Both overpressure and underpressure could be predicted according to opposite response characteristics, because of their opposite causal mechanisms. As for before drilling prediction, a new method called Geological statistics and analysis has been proposed by study, due to the low seismic Signal-to-Noise in deep layer and high exploration degre. As for the while drilling prediction and detection, dc exponent is the most common method because of its on-line, continuity and quantification, The basic reasons that affect its application results are the selection of trend line and appliance conditions. The methods combination and trend line determinated by sequence stratigraphy studied in this dissertition could solve such two questions. MR-ML could provide direct and relative precision porosity for fracture pressure caltulation, besides used for pressure prediction and detection. As for an given area, the overpressures are always caused by more than one mechanisms, and the reponses also have multiresolutions. So many abnormal pressure determination measures should be adopted to synthetically predict and detect abnormal pressures.