基于激发极化弛豫时间谱的浸染型海底多金属硫化物岩石物性评价方法

A physical property evaluation method of disseminated seafloor polymetallic sulfide rocks based on time domain induced polarization relaxation time spectra

海底多金属硫化物主要分布于洋中脊,是极具潜力的新型战略资源,其中以浸染型最难识别,探索有效的勘探评价方法必要且紧迫.弛豫时间谱起源于石油勘探中的激发极化测井,在金属矿尤其是海底多金属硫化物中的研究明显不足.本文将本征半导体极化理论引入原本以薄膜极化理论为基础的传统弛豫时间谱中,提出了一种评价浸染型海底多金属硫化物岩石物性尤其是激发极化特性的新方法,并通过理论和岩石物理实验数据的分析对比来验证方法的有效性.结果表明,该方法能有效评价浸染型海底多金属硫化物岩石的激发极化特性,包括对岩石弛豫时间常数、极化率等常规物性的评价,以及岩石中不同极化源的识别,此外还可以确定岩石中金属硫化物的含量和粒径;根据岩石物理实验结果,将海底多金属硫化物岩石的弛豫时间谱分为四种典型类型,能够反映多种分布形态的金属硫化物共存时岩石的激发极化特性;断电延时是影响激发极化特性评价的重要因素,稍大的断电延时就会导致浸染型金属硫化物的激发极化效应被大幅低估.该方法对海底多金属硫化物的激发极化测井解释具有指导作用.

Seafloor polymetallic sulfides mainly occur in mid-ocean ridges are increasingly regarded as strategic and promising metal resources for the future.One of the most difficult to detect in situ is disseminated seafloor polymetallic sulfide.It is necessary and urgent to search effective exploration and evaluation technologies.Relaxation time spectra(RTS)originated from induced polarization logging in petroleum exploration,the recognition and research on RTS of metal ore especially seafloor polymetallic sulfide is obviously insufficient.In this study,the theory of intrinsic semiconductor polarization was introduced into the traditional RTS based on membrane polarization theory and a physical property evaluation method for disseminated seafloor polymetallic sulfide rock was proposed.Synthesized and rock physics experiment data were calculated and analyzed to verify the validity of this method.The result shows that this method can effectively evaluate the induced polarization characteristics of disseminated seafloor polymetallic sulfide rocks,including the evaluation of conventional physical properties such as the relaxation time constant and chargeability,as well as the identification of possible polarization sources inside the rock.This method also can be used to evaluate the volume content and grain size of sulfide particles.Based on the rock physics experiment,the RTS of seafloor polymetallic sulfide rocks was divided into four typical types,which can indicate the induced polarization characteristics of rocks containing metal sulfides with multiple distribution.Delay duration is an important factor that affects the evaluation of induced polarization characteristics.Slightly larger delay duration can cause the induced polarization effect of disseminated metal sulfides to be greatly underestimated.This method has a directive function for the induced polarization logging interpretation of seafloor polymetallic sulfide rocks.