在海陆过渡带平缓斜坡沉积背景下，海平面升降频繁，导致砂岩、白云岩、石灰岩及混积岩在纵向与平面上呈现复杂的沉积特征，岩性分布规律尚不明确。以伊拉克B油田Asmari组为研究对象，通过岩心观察、显微薄片分析及钻测井资料综合解释，系统揭示了平缓斜坡背景下复杂岩性发育的主控因素。研究取得以下认识：①Asmari组岩性可划分为碳酸盐岩、混积岩和陆源碎屑岩3大类，其中混积岩又可细分为8类。基于岩石学特征与测井响应耦合分析，进一步识别出7种典型岩相组合序列。②岩相空间分布具有显著分带性。研究区西北部与东南部以碳酸盐岩相的同类组合为主，中部碎屑岩相的同类组合比例显著增加，其余过渡带不同类型混积岩相的组合占比较大。③研究区古地貌呈现“西北和东南低、中部隆起”的缓坡格局，古隆起主要发育陆源碎屑沉积，古洼地发育碳酸盐沉积，过渡斜坡带以混合沉积为主。最终建立了平缓斜坡背景下“古地貌形态—海平面波动—物源供给”三因素控制的复杂岩性发育模式。

The Asmari Formation in Iraq B Oilfield was deposited in a remnant ocean basin environment formed during the closure process of the Neo-Tethys Ocean. Influenced by the intermittent uplift of the Arabian Shield from the Oligocene to Miocene, the study area developed a multi-stage terrigenous clastic supply system. Under the depositional background of a gentle slope, frequent sea-level fluctuations have led to complex mixed sedimentary characteristics of sandstone, dolomite, limestone, and mixed rocks in vertical and planar distributions, whose lithological distribution laws remain to be further clarified. This study takes Iraq B Oilfield as the research object, and systematically reveals the main controlling factors of complex lithology development under the gentle slope background through detailed core observation, thin-section microscopic analysis, and comprehensive interpretation of drilling and logging data. The research has achieved the following understandings: (1) The lithologies of the Asmari Formation can be scientifically classified into three major categories: carbonate rocks, mixed rocks, and terrigenous clastic rocks. Among them, mixed rocks are further subdivided into 8 types based on the 50% ternary classification nomenclature; seven typical lithofacies combination sequences are identified through the coupling analysis of petrological characteristics and logging responses. (2) The spatial distribution of lithofacies shows significant zonation: the northwestern and southeastern regions of the study area are dominated by carbonate facies, the proportion of clastic facies in the central part increases significantly, and the mixed rock facies account for a large proportion in the remaining transition zones. (3) The paleogeomorphology of the study area presents a gentle slope pattern of "low in the northwest and southeast parts and high in the central part". The comprehensive tectonic-sedimentary analysis shows that terrigenous clastic sediments are mainly developed in the paleo-uplift area, carbonate sediments are developed in the paleo-depression area, and mixed sediments are dominant in the transitional slope zone. Finally, a development model of complex lithology controlled by three factors of "paleogeomorphic form—sea-level fluctuation—material source supply" under the gentle slope background is established.