低渗-致密储集层地层含气量估算方法及其应用

Method for estimating gas contentration in low permeability tight reservoir and its application

气测录井检测的是钻井液携带的地层烃类流体,是地下地质条件的直接反映,能有效鉴别地层流体性质。目前,由于钻井液含气量与气测检测值关系不明确,气测录井解释仍以定性解释为主。为了研究气测录井地层含气量解释方法,使用新设计的钻井液密封罐,从井场直接选取上返至井口且未经过气测检测设备的含烃钻井液,在实验室内开展真空加热全脱气实验,并进行气相色谱分析,计算得到钻井液含气量,结合现场气测全烃检测值,总结出钻井液含气量与气测全烃检测值的关系,据此将钻井参数转化成地层含气量,结合地层测试结论建立地层含气量的产能预测图板。分析认为,钻井液含气量主要为5~30 mL/L,钻井液含气量与气测检测值呈线性关系,计算所得的地层含气量一般为0.1~7 m^3/t,其中地层含气量大于2 m^3/t,地层测试证实为高产气层。经过实例验证,计算地层含气量与实际相符,地层含气量产能图板能有效地估算产能。

Gas logging detects the formation hydrocarbon fluid carried by drilling fluid,which is a direct reflection of subsurface geological conditions,and can effectively identify formation fluid properties.At present,because the relation between gas content in drilling fluid and the detection value of gas logging is not clear,the interpretation of gas logging is still characterized by the qualitative principle.In order to study the interpretation method of gas content in gas logging formation,the newly designed drilling fluid sealing tank was used to select the hydrocarbon bearing drilling fluid which returned upwards to the wellhead directly from the well site and did not go through the gas logging detection equipment.The vacuum heating complete degassing experiment and gas chromatographic analysis were carried out in the laboratory,the gas content of drilling fluid was calculated,combined with the total hydrocarbon detection value of field gas logging,the relationship between the gas content of drilling fluid and the total hydrocarbon detection value of gas logging is summarized.According to this,the drilling parameters are converted into the formation gas content,and the productivity prediction chart of the formation gas content is established based on the formation test results.The analysis shows that the gas content of drilling fluid is mainly 5-30 mL/L.There is a linear relationship between the gas content of drilling fluid and gas logging detection value.The calculated formation gas content is generally 0.1-7m 3/t,in which the formation gas content is more than 2 m 3/t,the formation test proves that it is a high-yielding gas layer.It is verified by examples that the calculated formation gas content is consistent with the actual situation,and the productivity chart of formation gas content can effectively estimate the productivity.