Fracturing in the Deep Zones at Yabase Oil Field

Abstract

This is the report about the outline of the effect of fracturing made against the deep zones of Yabase oil field during the three years of 1957, 1958 and 1959, wherein the relationship between the main factors and the effect of fracturing is examined by analysing the substance of fracturing-work in the producing wells.The greatest effect of fracturing was observed on the newly drilled wells. Namely, 69 new wells at Yabase oil field were fractured in these deep zones from July 1957 to the end of 1959, and the total production of these wells reached 112, 600 kiloliters during 10 months. As to the several wells where comparison was possible between the productions before and after the fracturing, this comparison proved that the production of new oil well had increased nearly twice as much due to fracturing.Fracturing effect in existing oil wells was not so conspicuous as in newly drilled wells, nevertheless, sure increase of oil production was evidenced. As the result of individual oil well examination, it became clear that the fracturing did not give much effect to nearly a half of the total fractured wells, but the increased production from the remaining half oil wells served in the considerable gains in the Company as a whole.In order to find the influence of respective fracturing factors, 51 producing wells in VIII zone of Koya, Sotoasahikawa, and VIIIab and IX zones of Yabase district were studied, figuring out the production increase after fracturing. As a result, we found that various factors are so entangled each other that each factor can not be discussed singly. However, the most significant factors are in the potentiality of reservoir properties. And secondly, such as the length of completion interval and injection rate have comparatively remarkable influence. However, direct influence of sand concentration and over flush was not clearly recognized.