Research On Volcanic Overflow Units Subdivision And Characteristics Of Volcanic Reservoir Development

The research on volcanic reservoir and oil accumulation, which has been neglected for along time, recently becomes a highlight in discovery of new hydrocarbon resources. Thispaper aims at research on volcanic overflow units and volcanic reservoir in the area ofChangle, Linqu and Kongdian formation in Weibei sag.This paper summerizes petrological features of igneous rocks through core observationand microscopic identification. It analyzes and identifies igneous rocks and sums up theircharacteristics of lithological change. The volcanic units are devided vertically based onlogging technology and field inspection and sampling data on outcrop area in Changle andLinqu region, as well as analysis of the lithology-electrical relationship of the work place. Themethod of classifying volcanic overflow units is proposed through a careful research in thearea of Changle, Linqu and Kongdian formation in Weibei sag, taking the abrupt change ofvolcanic rock lithology as standard, such as porosity, amygdaloid volcanic rock, thermalalteration heating of underlying rock, appearance of optalic metamorphism and sedimentaryintercalations. This systematic subdivision method of primary vocanic overflow units isnamed Three-band structure, refering to three different phase belts including upper phase ofvolcanic overflow phase, middle phase of volcanic overflow Phase and low Phase of volcanicoverflow phase. The classification of volcanic reservoir spaces of Changle, Linqu andKongdian formation in Weibei sag are divided into six types: intercrystal and intracrystaldissolved pores, air voids and its filling remnant voids, structural fissures, weathering fissures,and condensation shrinkage joint and so on. According to statistics on three different phases of reservoir physical properties of vocalnic rocks in Kongdian formation in Weibei sag, therelationship between volcanic overflow units phase and porosity and permeability has beenestablished, reservoir physical properties change regularly from deep to shallow part of theoverflow units, that porosity and permeability of upper phase of volcanic overflow phase arehighest, low Phase of volcanic overflow phase medium, and middle phase of volcanicoverflow Phase lowest.It is mainly hydrothermal activity, the volcanic lithofacies zone,fracturing, and weathering which are the key factors controlling the development of volcanicreservoir of Kongdian formation in Weibei sag. The prediction of favorable reservoir zone ismade through comprehensive analysis of reservoir controlling factors and overflow unitssubdivision.