## 2 Geological Background
### Deep Marine Environment, Processes and Lobe Complex  
Deep-marine siliciclastic deposits are vital for the petroleum industry, with respect to hydrocarbon exploration, with a gradual increase in exploration for huge petroleum discoveries in a large volume of deep-water sediments [34]. The development of these deep-marine deposits is the result of various sedimentary processes, which resulted in numerous architectural elements and sedimentary facies [35; 36; 37; 38]. In the deep marine environment, the components of a submarine fan are dependent on the distribution and variation of density flows and flow processes. Low-density turbidity flows are common in all subenvironments of deep-marine systems but are mostly abundant in the distal part of a submarine fan [39]. High-density flow processes are commonly associated with the feeder channels and distributary channels of a lobe in a submarine fan system. The variation in the thickness of sand units is also responsible for a variety of facies associations and depositional environments, such as the massive or thick-bedded sandstone with rare shale unit being most likely associated with the proximal lobe deposition. The lateral variation in the sedimentary succession of the individual lobe can be depicted from a decrease in the thickness of sand units with respect to neighboring shales, which represents the distal part of a submarine fan. The thickening up stacking patterns of lobes could be the result of the degradation of individual lobes [39; 40; 15; 41]. In order to understand the paleoenvironments and facies analysis, the classical Bouma sequence has limited applications for deep-marine lobe systems [26; 42]. Certain terminologies emerged in the past decade to refine the classification of deep-marine sediments. For example, the term \"hybrid bed\" is a product of the deceleration or transition of the turbidity current to mixed turbidite events [11; 43; 44]. Flow transformation is characterized by the erosion of underlying rock units within the feeder channels and the axial or proximal part of the lobe. The transition of flow from turbulent to laminar results in the development of heterogeneity in the form of hybrid beds, owing to the deceleration and expansion of flow [11; 44; 45]. Recent investigations explained that the deep-marine sand sheet or fan deposits included a feeder channel with several individual lobes [19; 46]. The relative age of each lobe may vary as the older lobe may be overlapped by the younger one (Figure 2), and this overlapping of lobes may continue in a lobe complex [19; 47]. The lobe complex can be classified based on the relative position of the feeder channel. Those present close to the feeder channel are termed as proximal lobes (Figure 2), the middle part of lobe complex is called the medial lobes, while those farther away from the medial lobes are labeled as distal lobes [24]. Lobes are divided into four subenvironments--the lobe axis, lobe off-axis, lobe fringe (both frontal and lateral) and distal lobe fringe--on the basis of the amount of sand, amalgamated surfaces and sedimentary facies [17; 45; 49; 50]. The lobe axis is predominantly composed of structureless, thick-to-massive bedded sandstone with amalgamation, indi  
Figure 2: Lobe terminology used for the discussion of facies heterogeneity and multiscale analysis of the lobe complex system. (**a**) Classification of the lobe complex into proximal, medial, and distal parts of the individual lobes [24; 46]. (**b**) Hierarchy of the lobe system, where the smallest unit is the bed or bed set while the largest unit is known as the lobe complex set [47] or lobe complex system. (**c**) Characterization of the lobe, with a feeder channel into the lobe axis, off-axis, fringe and distal fringe, each with representative logs [14; 19; 48]. cating greater depositional rates with high energy turbidity currents [17; 48].