| So far,most of the reservoirs in the world are in developing by artificial supply of energy. Methods used to observe the dynamics of reservoir is the base for all researches on the reservoir in this period. Most of the traditional methods for the observation are conducted in the well bore,such as well logs and well tests;the information obtained is limited in the region of near well bore. For the reservoirs of high heterogeneous,of long term flooded and of numerous production adjustments,only the way of well bore observation is not necessarily adapting to all the reservoir. Moreover,some special wells are also limited the use of well bore observations,such as horizontal wells,decline wells and high temperature wells.Interwell radiotracer test is a method that can obtain the information of reservoir in large scale. The other main features of the method are,it can be conducted during the production,no influence on the production and not critically rely on the technical status of the well.The basic procedure of an interwell radiotracer test is,to inject a proper radioisotope tagged tracer material into the injector together with the injected fluid;the tracer material will follow the injected fluid and go through the same path of injection fluid penetrating the formation;finally the tracer material will be produced at the producer;then,collecting samples at well head of producer,tracer response can be observed;by analyzing the response of tracer,the information on dynamics of injection fluid and reservoir geology can be obtained.The research and application of interwell tracer test has already a history of 40 years. Possibly because of the competition world and reservoir security,there are few open publications available in this field. From the limited source ofmaterials,we have found the development of this field can be summarized in three aspects,i.e. new tracers and their analysis methods,new developments on the interpretation of tracer response and new concepts & methods contributed on tracer methodology.Since 1980s,interwell radiotracer test has gained rapid development. The main reasons are radiotracers has the advancetages of high sensitivity,wide selectivity and no chemical contamination on the reservoir. Typical research institutions in this field are Corelab of USA,IFE of Norway and ICI TRACERCO of British,etc.The development of this field in China was started in late 1980s. In 1988,China Institute of Atomic Energy in cooperation with Daqing Oil Company conducted the first test using tritiated water as tracer for waterflood,opened the curtain of interwell radiotracer test in China. Since then,the author of this paper has been involved in and promoted the development of the field in China.The work of this paper described is based on two IAEA cooperation projects. One is the CRP project CPR//10114,the other is a model TC project CPR/8/010.Research work involved in this paper is in three aspects:1) new concept and new method of tracer test:the concept of Slight Disturbance Test (SDT) is proposed,the basic method of SDT is introduced. Main point of SDT is:when an interwell tracer test is conducting,the short-term changes of injection and/or production rates of the wells involved can generate abnormal tracer responses at the wells where tracer is already in producing;by analyzing the abnormal responses,information on flows produced at the production well from different directions can be obtained. It can be predicted that,if computer model and simulation techniques are employed for the interpretation of the abnormal tracer responses,formation parameters of near well bore region of the producer could be calculated. 2) methods on tracer analysis in oil filed brain:the methods used for four gamma emitting radiotracers and two beta emitting radiotracers are developed. 3) four real scale measurement of field tests are conducted andreported.According to the statistics of PetroChina,400 interwell tracer tests were conducted in 2001. The frequency of the test is already comparable to oth...
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