Abstract
The drilling time data of gas logging are used to calculate drilling time ratio of the reservoir, and the total hydrocarbon data are used to calculate hydrocarbon contrast coefficient and to establish the drilling time ratio--hydrocarbon contrast coefficient crossplot. The standards of distinguishing the boundaries of hydrocarbon zones, hydrocarbonaceous water layers and dry layers are determined according to the statistics of regional oil testing data. Based on the standards, the crossplot is divided into three areas: hydrocarbon zone, hydrocarbonaceous water layer and dry layer, which are used in mud logging interpretation of abnormal shows in oil and gas layers. This method is widely used for low-resistivity reservoirs, fracture reservoirs, shale gas layers, and especially in the oil and gas zone with weak show and a single component. It is more applicable and accurate than some conventional interpretation methods such as the triangle plot, PIXLER plot, dual light hydrocarbon alkyl ratio and hydrocarbons ratio (3H).
Highlights
It is adapted for unconventional oil and gas logging interpretation
The plot is divided into three areas: hydrocarbon reservoir, hydrocarbonaceous water layer and dry layer, which are used to characterize interpretation results
Through statistics of the regional data which have been proved to be hydrocarbon zone, hydrocarbonaceous water layer and dry layer by oil testing, the data points are plotted in RROP-Kc chart
Summary
How to find oil and gas show quickly and how to evaluate fluid properties during drilling has always been a problem concerned by global oil professionals. Modern gas logging uses high sensitivity automatic chromatographic gas instrument which uses chromatography to separate the takenoff gases They are measured by hydrogen flame ionization detector or thermal conductivity cell, the content and component of hydrocarbon gases and non-hydrocarbon gases are analyzed. The conventional methods for reservoir fluid property evaluation in gas logging and mud logging are triangular plot, PIXLER plot, dual light hydrocarbon alkyl ratio and hydrocarbons ratio (3H method) [8, 9] All of these methods require complete gas composition, and the C3 absolute percentage is more than 0.01% at least. According to the situation of low coincidence rate and inadaptability of the traditional methods, a fast interpretation method for reservoir fluid evaluation is proposed in this paper It is adapted for unconventional oil and gas logging interpretation
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