Research Of The Saturation Monitoring Of Remaining Oil Based On The PNN Log

After wells put into production, the production will change with the change of formation saturation. The oil and gas production tends to decrease and water cut rises sharply. The timely formation oil saturation monitoring, the water flooded formation understanding and evaluating as well as the next step in the oil and gas field production measures are significant to guide oilfield later rational development and improve the production efficiency. Due to the physical characteristics of the casing,openhole logging method has been a lot of restrictions which can not be used in cased hole formation evaluation. At present, most of cased-hole saturation logging methods are based on the principle of pulsed neutron logging nuclear logging methods, such as:the carbon-oxygen logging, neutron lifetime logging, boron neutron logging, PND logging, PNN logging,etc.In this paper, remaining oil evaluation based on YingMaiLi-YaHa oilfield is set as the research object. Doing some research based on PNN logging methods,and then discussing and analasing some problems in PNN logging interpretation as well as introducing effective interpretation model of remaining oil saturation to assess remaining oil flooded situation of the research area.PNN (pulsed neutron-neutron) logging technology is more advanced in the casing remaining oil saturation logging technology in recent years, which by far, nearly two He-3counter records the whole process from rise to fall in the time spectrum, thus extracting formation macroscopic capture cross section, determines the formation remaining oil saturation. PNN detecting thermal method, eliminates the method to detect gamma rays affect existing background values, low salinity and low porosity formation keeping count rate relatively high, so as to cut the influences of statistical fluctuation. At the same time, PNN also has a set of unique data processing method, can remove the greatest degree of borehole effect, guarantees the Sigma (formation capture cross section) curve accuracy. And the measurement of formation macroscopic capture cross section is the parameter of formation neutron characteristic, there is a good corresponding relationship between the lithology of reservoir and fluid properties, thus in the aspect of reservoir oil and gas layer identification and residual oil saturation evaluation, etc, has a unique advantage.This paper aims at the analysis from PNN logging process, adaptability evaluation of PNN logging tool in the research area, and the factors, a series of environmental impact by PNN logging process such as:to analyze borehole size effect, formation temperature effect, porosity effect, wellbore liquid effects, establishes the response relation chart between PNN logging capture cross section curve and the conventional logging curve, and according to the actual situation, determines the main control factors of block PNN logging, propose a more accurate correction method based on the block factors.Evaluated remainder oil saturation, through contrastive analysised the domestic and overseas existed saturation logging debice, based on the conventional volume model ptoposed the saturation interpretation model-improved volume model suit for the research area, and put forward a series of methods about how to get remainder oil saturation interpretation parameter(such as:framework capture cross section∑ma, argillaceous capture cross section∑sh, oil and gas capture cross section E h, formation water capture cross section∑w),for argillaceous capture cross section that is the most difficult to get in remainder oil saturation interpretation parameter,this paper puts forward the method which based on pure water layer of oil line and water line coincided, and example verified. On the whole to advanced the accuracy about interpret the remainder oil saturation, and it provides a reliable reference for next step swept layer evaluated.Swept layer evaluated part, combined with the oilfield water flooded layer level division standard at home and abroad, integrated adjacent blocks put forward a view water flooded layer level division standard suit for the study area. At the same time combination closely with the dynamic and static logging data of the block, with PNN logging interpretation saturation as the main line, combined with the output profile、 injection profile、completion interpretation results and so on, to analyse water flooded layer,which effectively improved the accuracy of the water flooded layer evaluation.Finally, based on the established model of the interpretation of the research area, the PNN log interpretation modules are made. Through the practical application, it is proved that it can be widely used in the oilfields.