The Study Of Reservoir Prediction And Fluid Identification In Reef And Shoal Reservoir In The East Of Pearl River Mouth Basin

There is large-scale marine carbonate deposition in Miocene of the east of Pearl River Mouth Basion. So large areas of carbonate have great potential for exploration, and after many years'exploration practice,we have discovered a batch of reef reservoir in carbonate ,such as LH11-1, LH4-1, LF22-1 oilfields etc which have huge reserves and wide exploration prospect. This paper's study district-HL exploration area is in the east of Pearl River Mouth Basion, but with the exploration into the medium term, the pure structural traps of carbonate have mainly been drilled, the key of the further exploration should be lithologic trap or lithological-structural traps, so the study and prediction of reservoir's distribution in carbonate is the key of exploration. But now using geophysical data for the prediction of reef and shoal reservoir is lack of effective forecast methods, the prediction and low success rate of drilling for reef and shoal reservoir is still lower.This paper taking the reef and shoal reservoir of the Zhujiang Formation in Miocene in HL area as the main study object,starting with the concept,classification and basic characteristics of the reef and shoa,conducts intensive study to the seismic response characteristics of reef and shoal reservoir, summarizes the internal, external, top and bottom seismic reflection characteristics and some recognition traps of reefs. By detailed description for the project location, regional tectonic characteristics, sedimentary facies, depositional model and sequence stratigraphic characteristics, makes full use of geological foundation research results, summarizes that the reef and shoal facies in platform margin of high water systems tracts is the most favorable area for reservoir development. Based on the analysis of the seismic data and geological, drilling, logging data fully collected from the study district, makes horizon fine calibration and contrast for intended formation, and uses neural network seismic waveform classification technology, seismic attribute analysis technique, impedance porosity inversion technique, the absorption attenuation analysis technology and multiattribute comprehensive analysis technique to forecast the distribution of reef and shoal reservoir, at the same time, proposes seismic prediction process suitable for the reef and shoal reservoir. First of all, study the seismic response characteristics of reef and shoal starting with the wave equation numerical simulation. Then, make full use of geological foundation research, analyze the favourable sedimentary facies belts and stratigraphic sequence, conduct seismic facies division using neural network method and set up the relationship between sedimentary facies and seismic facies, find the favorable development area of reef and shoal reservoir. On this basis, apply the appropriate methods of reservoir detection and fluid identification, such as seismic attribute analysis, post-stack wave impedance inversion, porosity inversion, low frequency shadow and frequency attenuation gradient to reservoir prediction and fluid identification, conduct the comprehensive prediction of reef and shoal reservoir combining with geological, logging and development data.By the above analysis,this paper has made the following major achievements and understanding:In the geological aspects,①makes full use of geological foundation research results, knows the factors of reef and shoal development and distribution,and the influence of the sequence stratigraphy principle to the development of the reef and shoal reservoir owned different physical properties.②in the control factors of reef and shoal development,based on seismic data,establishes the seismic facies mode of reef and shoal, and the relation between seismic facies and sedimentary facies, macroscopically summarizes exploration prospects area.③by the integrated prediction of a variety of methods, forecasts a favorable area(located at a relatively high structural position). In the aspects of methods and technology,①for the seismic response characteristics of reef and shoal reservoir, conducts reservoir comprehensive prediction with geological, drilling, logging data, proposes a forecast flow suitable for reef and shoal reservoir in this study district.②proposes a new way which combines with impedance inversion, frequency attenuation gradient and low frequency shadow technology to fine depict reservoir and increase the prediction accuracy. That is because impedance inversion has high resolution in vertical and can identify the reservoir thickness, the two time-frequency analysis methods that low frequency shadow and frequency attenuation gradient not only can identify the fluid, but also predict the reservoir's horizontal distribution.To sum up, the above methods have achieved good results, laid a certain foundation for accurately predicting the distribution rang of reef and shoal and favorable reservoir distributioncan, offered evidence for the following drilling deployment, also accumulated some experience for the prediction and fluid identification of other reef and shoal reservoir with the similar seismic, geological conditions.