PNNPlus饱和度测井技术在胜利油区剩余油评价中的应用研究

Application Research of PNNPlus Saturation Logging Technology in Residual Oil Evaluation in Shengli Oilfield

摘要: 胜利油区已进入开发中后期，长期注水开发导致储层水淹程度加剧，剩余油分布更加零散复杂。准确识别剩余油富集层段、评价水淹级别，并为补孔、封堵、改层和压裂等措施提供依据，是老油田精细挖潜的重要基础。目前，剩余油评价主要依赖常规测井、碳氧比测井、脉冲中子俘获测井及PNN饱和度测井等方法。其中，PNN技术通过宏观俘获截面Sigma反映地层含水状况，在套管井剩余油监测中具有较好适用性，相关研究已在复杂水淹层识别、解释参数确定及现场应用方面取得一定进展。但在胜利油区实际应用中，传统PNN方法仍存在不足：低矿化度条件下油水俘获差异减小，高矿化度条件下井筒背景干扰增强，泥质含量、孔隙度和岩性非均质性也会影响Sigma响应，单一参数解释容易造成水淹级别误判。PNNPlus是在传统PNN基础上的改进技术，通过增加活化伽马探测短节，实现热中子俘获截面与活化伽马能谱信息的联合采集，为复杂储层条件下剩余油评价提供了新的手段。本文结合胜利油区地质与开发特征，建立以Sigma为核心，融合GR-SIGMA交会分析、泥质校正、孔隙度修正和地层水矿化度参数的PNNPlus综合解释方法，并通过常规老井、低孔隙度井、高矿化度井、低矿化度井及新投井实例验证其适用性，为胜利油区剩余油精细评价和开发调整提供技术支持。

Abstract: The Shengli Oilfield has entered the middle and late stages of development. Long-term waterflooding development has aggravated reservoir water flooding and made the distribution of remaining oil more scattered and complex. Accurately identifying enriched intervals of remaining oil, evaluating water flooding levels, and providing a basis for well stimulation measures such as perforation replenishment, water shutoff, layer reworking and fracturing constitute an important foundation for fine potential tapping in mature oilfields. At present, the evaluation of remaining oil mainly relies on conventional logging, carbon-oxygen ratio logging, pulsed neutron capture logging, PNN saturation logging and other technologies. As a technique reflecting formation water cut through the macroscopic capture cross-section Sigma, PNN is well applicable to remaining oil monitoring in cased wells. Relevant researches have made certain progress in the identification of complex water-flooded layers, determination of interpretation parameters and field application. Nevertheless, the conventional PNN method still has limitations in the practical application of the Shengli Oilfield: the difference in capture cross-section between oil and water decreases under low salinity conditions, while borehole background interference increases under high salinity conditions. In addition, shale content, porosity and lithological heterogeneity also affect the Sigma response, and interpretation relying on a single parameter is prone to misjudgment of water flooding levels. PNNPlus is an improved technology developed on the basis of conventional PNN. By adding an activated gamma detection sub-section, it realizes the combined acquisition of thermal neutron capture cross-section and activated gamma spectrum information, providing a new approach for remaining oil evaluation under complex reservoir conditions. Combined with the geological and development characteristics of the Shengli Oilfield, this paper establishes a comprehensive PNNPlus interpretation method centered on Sigma, integrated with GR-SIGMA crossplot analysis, shale correction, porosity correction and formation water salinity parameters. Its applicability is verified by case studies of conventional old wells, low-porosity wells, high-salinity wells, low-salinity wells and newly commissioned wells, which provides technical support for fine remaining oil evaluation and development adjustment in the Shengli Oilfield.