基于岩相的酸性火山岩储层流体识别方法

松辽盆地徐深气田火山岩岩相不仅类型多样,而且还控制着岩性的成因和孔隙结构类型,使得应用中子—密度测井曲线交会和电阻率的高低来识别储层流体性质的效果变差。为此,探讨了该区火山岩流体识别的问题:对不同岩相储层的岩性和孔隙结构特征进行分析后,将成因和测井响应特征相近的岩相归类为爆发相和溢流相;然后根据储层含天然气时在测井响应上的特征,在四性关系研究和岩相识别的前提下,先用三孔隙度、核磁共振及横纵波时差等曲线特征识别储层的含气性,把水层(包括高阻水层)和含气储层分开;进而分岩相建立了火山岩储层流体识别标准,据此识别出气水同层(包括高阻同层)和气层。运用该识别方法对徐深气田的21口新井39个层位进行流体识别和试气验证,结果表明:识别准确率达89.1%,提高了近12%。结论认为,分岩相建立流体识别标准的方法不仅适用于徐深气田酸性火山岩储层的流体性质识别,而且对于其他岩相复杂火山岩或沉积岩储层流体识别也具有借鉴意义。

A lithofacies-based fluid identification method for acidic volcanic rock reservoirs: Case history of the Xushen Gas Field,Songliao Basin

In the Xushen Gas Field, Songliao Basin, there are multiple types of volcanic rock facies, which control the genesis of reservoirlithology and the type of pore structure, so reservoir fluid properties cannot be better identified by applying the neutron-density loggingcurve intersection and the value of resistivity. In this paper, therefore, the fluid identification method for volcanic rocks in this area wasdiscussed. First, after reservoirs of different lithofacies were analyzed in terms of lithology and pore structure characteristics, the lithofacieswith the similar origins and logging response characteristics was classified as eruptive facies and overflow facies. Then, according tothe characteristics of natural gas in the logging response, the gas-bearing property of reservoirs was identified by using the curve characteristicsof porosity combination, NMR (nuclear magnetic resonance) and shear-compressional wave slowness ratio so as to distinguishaquifers (high-resistivity aquifers included) from gas-bearing reservoirs, after the four-property (lithology, physical property, hydrocarbonpotential and electric property) relationship study and lithofacies identification were completed. Finally, a fluid identification standard forvolcanic reservoirs was established on the basis of each lithofacies, and accordingly, gas–water layers (those with high resistivity included)and gas layers were identified. This method was applied in the Xushen Gas Field for fluid identification and gas testing of 39 intervals in21 new wells. It is shown that the identification accuracy (up to 89.1%) is increased by 12%. And it is concluded that the lithofacies-basedfluid identification method is not only applicable to the fluid property identification of the acidic volcanic reservoirs in the Xushen GasField, but also acts as reference for the fluid identification of volcanic or sedimentary facies with more complicated lithofacies.