四川盆地天然气录井特点与识别方法

四川盆地天然气录井具有隐蔽性强的特点，使过平衡钻井中不易识别、发现气层，易发生井漏与井喷，对产层的解释评价也有一定难度。为此，总结和归纳了四川盆地天然气录井特点与识别方法：在常规钻井条件下的天然气识别方法主要靠气测，辅之以钻时、岩屑录井技术，并及时进行小层对比，以确保发现储层。欠平衡钻井的天然气识别方法主要有4种：①气测录井仍是判断油气显示的主要依据；②精细分析钻时，从微弱变化中明查储层；③正确录取和鉴别岩屑是及时发现储层的关键；④及时观察出口工程参数及火焰的变化，是发现气层的佐证。天然气录井中的井控工作包括：搞好地质预报预告，及时发现油气水漏显示与预警，加强坐岗记录以保证钻井安全。

CHARACTERISTICS OF LOGGING AND RECOGNITION METHODS OF GAS LAYERS IN SICHUAN BASIN

Well logging in the Sichuan Basin is characterized by strong elusiveness. Recognition of gas layers is difficult during overbalanced drilling, lost circulation and blowout can occur easily, and interpretation and evaluation of pay zones are also somewhat difficult. This paper summarizes the characteristics of logging and recognition of gas layers in the Sichuan Basin. For conventional drilling operation, recognition of gas layers mainly depends on mud logging, with drilling time log, sieve residue log and sublayer correlation as supplements. For underbalanced drilling, there are 4 methods of recognizing gas layers: ① Mud logging is still the main basis of recognizing oil/gas shows; ② Detailed analysis of drilling time can reveal fine changes, according to which reservoirs can be identified; ③ Correct sampling and discrimination of cuttings are the key to timely recognize reservoirs; ④ Observations of changes of outlet parameters and flame can verify the recognized gas layers. Well control measures in the process of logging include strengthening geologic prediction, timely finding and early warning of oil/gas/water leakage, and strengthening records, so as to ensure safe drilling.