フラクチャー型貯留層を有する堆積盆地解析の試み

抄録

Petroleum explorations become more difficult recently, because its target is deeper and the trap types are more, complicated. This paper presents discussion about timing between formation of deep-seated fracture reservoir and trapping hydrocarbon (generation, migration and accumulation) in an area of the Hokkaido region.
Tectonic stress is thought to be a main driving force of fracturing. In this tectonic simulation, formation and development of fracture in every sedimentation step is reproduced by using Virtual Basement Displacement Method (KODAMA et al., 1985). The plastic strain that formed fractured reservoir tends to concentrate in the surrounding area of Well A during all the geologic time except a period of depositing e formation. On the other hand, there are not so significant concentration around Wells B and C through the time. It can be thought that Well A and its surrounding area seem to be favorable for forming fractured reservoir.
For the hydrocarbon generation, migration and accumulation simulation, large permeability value is input to a position of large plasitic strain observed by the tectonic simulation in order to investigate effect of tectonic fracturing. It is an evidence from the experiments by the model that fluid pressure around Well D should increase without tectonic fracturing whereas no excess pressure would be observed in the case that tectonic fracturing has occurred. This result is supported by the fact that density logging from Well D shows that all the data are plotted on the normal trend and there are no indication for abnormal pressure while drilling. Gas saturation around Well A is also higher as a result of effective flow into the reservoirs by the tectonic fracturing. The peak of generation rate of oil and gas exist during the period of depositing d formation and e formation.
As a conclusion of the study of these simulations, the area has enough hydroacarbon generation potential. However, focusing on formation of the trap (fractured reservoir), Well A and its surrounding area has a possibility of forming fractured oil and gas field.