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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 66 (1982)

Issue: 5. (May)

First Page: 611

Last Page: 611

Title: Previous HitEstimationNext Hit of Paleo-Pore Pressure and Time of Hydrocarbon Expulsion--Computerized Simulation Previous HitModelNext Hit: ABSTRACT

Author(s): Kazuo Nakayama, Tadao Hoizumi

Article Type: Meeting abstract


A geological simulation Previous HitmodelNext Hit of generation and expulsion of hydrocarbon can be a useful tool in hydrocarbon exploration. The advantage of the Previous HitmodelNext Hit is to realize different environments in which hydrocarbon accumulations form under various geologic conditions.

A geologic cross section of an area is divided into a series of vertical columns, which are sectioned into rectangular cells. The Previous HitmodelNext Hit simulates the various geologic processes during basin development: (1) burial compaction of sediments, (2) history of temperature estimated from thermal conductivity and heat flow, (3) Ro (vitrinite reflectance) value calculated by Lopatin's method, and (4) the amount of generated hydrocarbon as a function of generation potential and of transformation ratio represented by Ro. Increase of pore pressure is assumed to be caused by (1) increase of Previous HitoverburdenNext Hit, (2) increase of volume of free water resulted by clay dehydration, (3) aquathermal expansion of water, and (4) expansion of fluid phase by hydrocarbon generation. Residual pore ressure in each step of geologic time in the Previous HitmodelNext Hit is calculated by Rubey-Hubbert's equation:

PA = kT + (Po - kT) . e-tT/

where PA = residual abnormal pressure, Po = initial abnormal pressure, k = ratio of pressure increase, t = duration, and T = relaxation constant. T is a function of permeability that is derived from porosity and grain size. The amount of hydrocarbon expelled is calculated from residual abnormal pore pressure as a function of relative permeability and viscosity of fluids. Direction and time of hydrocarbon migration can be interpreted from spatial distributions of paleo-pore pressure and of hydrocarbon expelled from source rocks for each geologic time.

The Previous HitmodelTop is applied to the Niigata sedimentary basin of the coastal region of the Sea of Japan. Regional differentiation of time of hydrocarbon accumulation in the basin is observed. Upward hydrocarbon migration across the strata is also implied at culminations of the trapping structures.

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Copyright 1997 American Association of Petroleum Geologists