不同泥浆体系下东海低渗储层测录井评价

Logging evaluation for low permeability reservoirs under different mud systems in East China Sea

东海油气资源丰富,其中低孔低渗储层的油气资源占比约2/3,勘探前景广阔。在勘探期间,偶尔见储层物性相对较好,低产的现象。为了明确储层低产的原因,改善储层的产能问题,研究发现水基泥浆对油气层有着不可逆的污染现象,为此东海推行油基泥浆新体系。在新泥浆体系下,测井和录井等资料采集的环境发生改变,油基泥浆环境下,油气层与水层的侵入现象与水基泥浆完全相反,油气层无侵入,水层侵入明显;录井中气测组分以及荧光信息受油基泥浆影响较大,气测组分容易被油基泥浆吸收,并且荧光信息混杂有泥浆荧光,因此,对油气水层识别及定量评价不能忽略油基泥浆带来的影响。本文对比不同泥浆环境下测录井资料解释方法的差异,为东海建立快速有效的油气识别方法提供依据。

The East China Sea has rich oil and gas resources,in which the low porosity and low permeability reservoirs account for two-thirds of the total and hence are of great importance for exploration.It is occasionally found during exploration that some of the reservoirs have good physical properties,but low production.Efforts have been made to find out the reasons for such a phenomenon and the ways to improve the productivity.Our study found that water-based mud has irreversible pollution to the oil and gas reservoir,and thus oil-based mud is recommended.In the new mud system,the environment for well logging and mud logging are opposite.In the environment of oil-based mud,the invasion phenomenon is completely different for oil-gas reservoir and water reservoir.For oil and gas reservoirs,there is no mud invasion.For water reservoirs,however,mud invasion is common.Besides,the mud environment has great impact on the component of gas logging and fluorescence data.Some of the components may be absorbed by oil based mud and the fluorescence disturbed.In conclusion,the influence of oil based mud can not be ignored,when identification and quantitative evaluation are made for oil,gas and water reservoirs.By comparing some well logging and mud logging interpretation methods in different mud environment,we have established in this paper a fast and effective method for identification of oil and gas reservoirs in the East China Sea.