黄河口凹陷缓坡带东营组溢流相分布特征研究及钻井工程应用意义

黄河口凹陷缓坡带东营组广泛发育以溢流相玄武岩和凝灰岩为主的火成岩，此类岩石较为坚硬，钻进时易出现钻速低、井漏、井塌等问题，对钻井工程影响较大。综合利用录井、测井资料对东营组一段和二段火山喷发旋回和期次进行识别和划分，并结合地震资料对BZ34-9火山溢流相进行精细刻画。研究表明:研究区火成岩主要分布于BZ34-9和KL4-2构造区的共轭走滑断裂带，以裂隙式火山喷发为主；东营组一段和二段可识别和划分6个喷发旋回16个喷发期次；东二下段早期和东一段早、晚期喷发旋回规模较小，东二下段晚期和东二上段早、晚期喷发旋回规模较大，反映了火山活动由弱增强再逐步减弱的发育过程。进一步，在复杂断层、地层模型构建的基础上，结合构造应力场模拟，预测地层力学薄弱带或裂缝发育特征，为开发井轨迹优化以及钻具、钻井参数、钻井液优选提供可靠依据。

Distribution characteristics and drilling engineering significance of Dongying Formation overflow facies in the gentle slope belt of Huanghekou Sag

Igneous rocks dominated by basalt and tuff of overflow facies are widely developed in the Dongying Formation in the gentle slope belt of Huanghekou Sag. This type of rocks are relatively hard and tend to suffer low rate of penetration (ROP), circulation loss, hole collapse and other problems in the process of drilling, which have greater impact on drilling engineering. In this paper, the volcanic eruption cycles and stages in the first and second Members of Dongying Formation (Ed₁ and Ed₂) were identified and divided by using mud logging and wireline logging data comprehensively. And combined with seismic data, the volcanic overflow facies in BZ34-9 block was described precisely. It is indicated that the volcanic rocks in the study area are mainly distributed in the conjugate strike-slip fault zone of BZ34-9 and KL4-2 structure zones, where fissure type volcanic eruption is dominant. Six eruptive cycles and sixteen eruptive stages can be identified and divided in Ed₁ and Ed₂. The eruptive cycles in the early stage of lower Ed₂ and the early and late stages of Ed₁ are small sized while those in the late stage of lower Ed₂ and the early and late stages of upper Ed₂ are large sized, which reflects the growth process of volcanic activity from weak to strong and then weak gradually. Based on the construction of complex fault and formation model, combined with the simulation of tectonic stress field, geomechanically weak belts or fracture development characteristics can be predicted, which provide reliable basis for the trajectory optimization of development wells and the selection of drilling tools, drilling parameters and drilling fluids.