Open Geosci. 2018; 10:866–881 Research Article Open Access Jinkai Wang*, Zhang Jinliang, and Jun Xie Analysis of the Factors that Influence Diagenesis in the Terminal Fan Reservoir of Fuyu Oil Layer in the Southern Songliao Basin, Northeast China https://doi.org/10.1515/geo-2018-0068 Keywords: Songliao basin, ultra-low permeability, termi- Received April 26, 2018; accepted November 8, 2018 nal fan, pore type, diagenesis Abstract: The diagenesis mechanism and the physical properties of a terminal fan reservoir are determined by nuclear magnetic resonance (NMR), X-ray diffraction and 1 Introduction scanning electron microscopy. The main provenance di- rections are NE and SE, and the two oppositely directed 1.1 Background fans converge to form a small catchment basin. The mud- stone color is red or purplish red, which accounts for Little controversy exists regarding the sedimentary sys- 60% of the total rock. The sandstones are lithic-feldspar tem that produced the fourth member of the Quantou for- sandstones and feldspar-lithic sandstones, with a smaller mation in the Songliao basin; most researchers consider quartz component relative to the adjacent sandstone for- this formation to be a shallow water delta, which is a mations. The reservoir mainly consists of intergranular lake delta model formed in a dry environment, the main pores (51%), intragranular pores (22%), corrosion pores types of sedimentary facies are channel, channel flood, (20%), micro-fractures (5%) and clay matrix pores (2%). sand bar, levee, crevasse splay and sand sheet [1–6]. A The porosity of the reservoir is only 13%, and the throats few researchers, such as Peng and Gong, hold other views, are fine with high displacement pressure. The diage- defining it as a common delta front [7, 8]. Sun thought it netic processes included compaction, cementation, re- was a meandering river delta, because of the control of placement, and dissolution, and the most influential fac- the sedimentary system of the meandering river delta in tor on the reservoir porosity was compaction. The detri- the northwest provenance, the southern part of Songliao tal rock cement mainly consists of clay minerals (48%), Basin mainly developed a large area of thin sand bodies quartz (23%), carbonate (19%), feldspar (7%) and daw- distributed in large areas [9]. Wang thought that the low sonite (3%). Among them, the mixed I/S layer has the most delta sedimentary facies was developed in the southern content and the most important cementation. In addition, Songliao basin. During this period, the uplift rate of the a small amount of dawsonite is found in the pores of the provenance decreased, and the water system was shrink- sandstone, which is a unique mineral that is related to the ing to the land, the lake basin expanded, and the sed- background of inorganic CO2. The main diagenesis factors iment source came from the surrounding mountainous that affected this sandstone’s porosity were compaction, early quartz overgrowth and calcite cementation, which reduced the porosity from 40% to approximately 8%. Al- *Corresponding Author: Jinkai Wang: College of Earth Science though dissolution and fracture increased the porosity and Engineering, Shandong University of Science and Technology, (from 8% to 26%), clay- and carbonate-mineral cementa- Qingdao, 266590, China tion during the late diagenesis period had a dramatic ef- Laboratory for Marine Mineral Resources, Qingdao National Labora- fect, forming a typical low-porosity and low-permeability tory for Marine Science and Technology, Qingdao 266237, China Jun Xie: reservoir. College of Earth Science and Engineering, Shandong Uni- versity of Science and Technology, Qingdao, 266590, China Laboratory for Marine Mineral Resources, Qingdao National Labora- tory for Marine Science and Technology, Qingdao 266237, China Zhang Jinliang: College of Earth Science and Engineering, Shan- dong University of Science and Technology, Qingdao, 266590, China College of Resources Science and Technology, Beijing Normal Uni- versity, Beijing 100875, China Open Access. © 2018 Jinkai Wang et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution- NonCommercial-NoDerivs 4.0 License. Analysis of the Factors that Influence Diagenesis in the Terminal Fan Reservoir Ë 867 area [10].However, the latest research showed that the sed- vision is not sufficiently fine [16]. Newell studied the sedi- imentary characteristics of this region are unique, unlike a mentary characteristics of Permian strata in the southern common river delta. These features are reflected in aspects Ural River in Russia to better understand each terminal such as the lithology, mudstone color, grain size, sand- fan facies and divided the facies into various micro depo- body extension law and so on. sitional environments [17]. This research provided an im- Therefore, a new terminal fan sedimentary system has portant theoretical basis to deepen the study of terminal been proposed. A terminal fan is a special fluvial-delta sed- fan sedimentary systems. Parkash classified the terminal imentary system that forms in a dry to semi-dry environ- fan system of the Makanda River in India into three sec- ment, where the flow rate is reduced at the end of the river. ondary sedimentary environments, namely, channel, nat- With the gradual decline in terrain slope, water spreads ural levee and flood plain, and identified nine lithofacies. out and the flow rate drops, allowing a large amount of This is a detailed anatomical study of the end fan sys- clastic material to be deposited to form the fan-shaped ac- tem [18]. Sanchez constructed a model for a terminal fan cumulation. The terminal fan is different from the alluvial sedimentary system from the lower Cretaceous Candeleros fan, diluvial fan and turbidite fan, they are not the same formation in the Neuquen basin, dividing the sedimentary type. The rocks deposited by terminal fan are usually finer body into three components from bottom to top, but this in grain size, better in sorting, and have higher component classification method was not conducive to the fine-scale maturity and textural maturity. The terminal fan is similar evaluation of reservoirs [19]. Chatmas conducted a series to the river delta, the difference between them is whether of experiments with controlling variables including mo- there is a stable catchment area at the front of the fan body. bile substrate thickness, sediment supply rate, and basin River deltas are generally pushed into stable water bodies, slope, in order to reveal the sedimentary origin and in- forming sediments interacted by rivers and lakes (oceans). fluence factors of the terminal fan. The results indicated However, the front end of the terminal fan usually does not that a higher sediment discharge rate on a substrate re- have a stable catchment area, or its size changes rapidly sulted in faster fan progradation coupled with relatively with the season, so, the terminal fan would disappear be- less subsidence and more sediment transport to terminal fore entering the water at the end [11]. The microfacies of channels [20]. the terminal fan is defined as four different types in this pa- With the deepening study of reservoir characteristics, per: distributary channel, near channel overflow, far chan- increasing numbers of researchers support that sedimen- nel overflow and mud flats, and this view is different from tary facies can greatly influence the types of rock diagen- that of previous studies. esis [21]. Klunk revealed that diagenetic reactions, which Mukerji first proposed the concept of a sedimentary are characterized by the dissolution and precipitation of fan based on a study of the Sutlej-Yamuna plain [12]. Later, minerals at low temperatures, control the quality of sedi- Friend studied the Devonian-age red sandstone and pro- mentary rocks as hydrocarbon reservoirs [22]. Mansurbeg posed a model for terminal fan deposition from many analyzed the mineralogy, petrography and geochemistry present-day river systems that have been studied. This lit- of siliciclastics to decipher and discuss the diagenetic al- erature was the first that studied terminal fan sedimen- teration and subsequent evolution of reservoir quality and tary deposits but proposed a dry environment for the ter- determined that the carbonate cements were of eogenetic minal fan sedimentary model, and its specific sedimen- and mesogenetic origin [23]. Gahtani studied the influ- tary pattern was not described [13]. Some objections were ence of diagenetic alterations on porosity in the Triassic also raised, North argues that modern rivers in arid re- Narrabeen Group, he studied the rock type and pore struc- gions cannot bifurcate in the lower reaches of the river, ture of the reservoir with a large number of analytical and that the so-called branching rivers are caused by con- and laboratory data (casting thin section, scanning elec- tinuous channel changes, which can also be seen in some tron microscope, X-ray and so on), and divided the dia- large alluvial fans [14]. Zhang found a widely developed genesis stage in detail, and analyzed the relationship be- red mudstone layer with shallow water and oxygen-rich la- tween oil-bearing property and pore structure of the reser- custrine facies, naming it flood rock. This research laid the voir [24]. Yuan studied the diagenesis of sandstone by us- foundation for the application of the terminal fan model ing microscopic analysis techniques and suggested that in a continental lake basin in China [15]. Kelly et al. di- leached feldspars were the internal source of authigenic vided terminal fans into three zones, namely, the recharge quartz [25]. Mork discussed the diagenesis and quartz ce- channel, distributary channel and remote basin, accord- ment distribution of low-permeability sandstones, he be- ing to a study of the Devonian formation in England. This lieves that the main factor contributing to the low perme- view is similar to that in this article, but the degree of di- ability of rocks is the large amount of silica cementation, 868 Ë Jinkai Wang et al.