文昌B凹陷北坡珠海组潮汐沉积特征及演化

文昌凹陷珠海组是重要的含油层系，但目前缺乏对文昌B凹陷北坡珠海组沉积特征的系统性研究，制约了该地区进一步勘探。以钻测井、岩芯、分析化验以及地震等资料为基础，对文昌B凹陷北坡珠海组进行层序地层划分、地震相识别、沉积特征及其演化分析。综合研究表明，珠海组发育三个三级层序；研究区广泛发育潮汐复合层理、双向水流的羽状交错层理以及强烈的生物扰动和虫孔等构造，为典型潮坪的潮间带和潮下带沉积；在三个地震层序中识别出7种典型地震相并建立地震相与沉积相响应关系，以对沉积相展布进行研究；早渐新世末，海水开始侵入盆地，由于神狐隆起的障蔽作用，其沉积主要受潮汐作用控制，伴随海侵的进行，沉积了珠海组厚层的潮坪沉积，此后海侵进一步加剧，障壁逐渐消失，波浪作用增强，逐渐过渡到新近系正常滨浅海沉积；各层序高位体系域的潮下带和潮间带砂坪沉积与其上泥坪沉积和海侵浅海泥沉积组成良好的储盖组合，其中潮汐水道和水下沙坝楔形沉积体为砂体较厚、分选好的优质储层，也是下一步勘探的有利目标。

Tidal Sedimentary Characteristics and Evolution of the Zhuhai Formation,Northern Slope of the Wenchang B Sag

The northern slope of Wenchang B Sag lies between the Sag and the Qionghai Uplift， With the deepening of exploration， the breakthrough in this area becomes increasingly important. The Zhuhai Formation is an important oil bearing formation in the Wenchang area， but the lack of systematic research on the sedimentary characteristics of Zhuhai Formation in the area has limited further exploration. Firstly， the sequence interface was identified， and the Zhuhai Formation was divided into three long?term cycles and six intermediate cycles by high?resolution sequence stratigraphy based on core， logging and seismic data. The stratigraphic sequence was divided to identify the seismic facies and analyze the sedimentary characteristics and evolution of the Zhuhai Formation. A comprehensive study has shown three sequences: tidal complex stratification， pinnate cross?stratification of two?way flow， and strong biological disturbance and wormhole structures widely developed in the study area， which are intertidal and subtidal deposits typical of tidal flats. Seven typical seismic facies were identified from the three seismic sequences， and the relationship between the seismic and sedimentary facies was established to study their distribution. During deposition of the three sections of the Zhuhai Formation， seawater began to invade the basin. Due to the obscuration by the Shenhu Uplift， the sediment was controlled by tidal action， and was mainly deposited in the subtidal and intertidal zones. A short source fan delta was deposited at the margin of the bulge. The tidal effect of the second section of the Zhuhai Formation was strengthened， producing a subtidal zone which is widely distributed throughout the study area. During initial Zhuhai Formation deposition， the barrier gradually disappeared as the transgression intensified； tidal action gradually weakened， and the intertidal zone became more relatively developed. Subsequently the transgression was further intensified and gradually transitioned to normal shore?neritic sediments in the Neogene system. The subtidal and intertidal sand flat deposits of the high sequence system tract， and the upper mud flat deposits， or transgressive shallow sea mud deposits， now constitute a good reservoir caprock. The tidal channel and wedge?shaped underwater bar sedimentary sand bodies are thick and well sorted， and are likely to be high?quality reservoirs and favorable exploration targets.