GeoScienceWorld Lithosphere Volume 2021, Article ID 2609923, 14 pages https://doi.org/10.2113/2021/2609923 Research Article Densification and Fracture Type of Desert in Tight Oil Reservoirs: A Case Study of the Fuyu Tight Oil Reservoir in the Sanzhao Depression, Songliao Basin Binchi Zhang ,1,2 Dejiang Kang ,3 Shizhong Ma ,4 Wenze Duan ,1 and Yue Zhang 5,6 1School of Earth Sciences, Northeast Petroleum University, Daqing 163318, China 2Heilongjiang Oil and Gas Reservoir Forming Mechanism and Resource Evaluation Key Laboratory, Northeast Petroleum University, Daqing 163318, China 3Exploration and Development Research Institute, Daqing Oil Field Co., Daqing 163712, China 4Bohai-Rim Energy Research Institute, Northeast Petroleum University, Qinhuangdao 066004, China 5College of Geosciences, China University of Petroleum, Beijing 102249, China 6State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Beijing 102249, China Correspondence should be addressed to Dejiang Kang; [email protected] Received 18 April 2021; Accepted 17 June 2021; Published 19 July 2021 Academic Editor: Hao Liu Copyright © 2021 Binchi Zhang et al. Exclusive Licensee GeoScienceWorld. Distributed under a Creative Commons Attribution License (CC BY 4.0). The exploration of unconventional oil and gas, especially the exploration process of tight oil, is closely related to the evolution of tight reservoirs and the accumulation process. In order to investigate the densification and accumulation process of the Fuyu tight oil reservoir in the Sanzhao depression, Songliao Basin, through the new understanding of reservoir petrological characteristics, diagenesis and diagenetic sequence are combined with a large number of inclusions: temperature measurement, spectral energy measurement, and single-well burial history analysis, and then contrastive analysis with current reservoir conditions. The results prove that diagenesis is dominated by compaction and cementation, and the restoration of paleoporosity shows that its porosity reduction rate reached 67% and the densification process started in the early Nenjiang Formation and was finalized at the end of the Nenjiang Formation. The accumulation of the Fuyu oil layer generally has the characteristics of two stages and multiple episodes, and the main accumulation period is the end of the Mingshui Formation. The end of the Nenjiang Formation, where the main body of the reservoir is densified, is just a prelude to the massive expulsion of hydrocarbons in the Songliao Basin, which makes the Fuyu oil layer have the characteristics of first compacting and then accumulating. Through the above analysis, it can be seen that the accumulation of oil and gas in the Fuyu oil layer, Sanzhao depression, is more dependent on the fault-dominated transport system. In addition, it is believed that tight oil accumulation should have the characteristics of short-distance oil enrichment around the fault, and the development area of fracture deserts near the fault sand body should be the key area for further exploration. 1. Introduction resource abundance, locally developed sweet spots, and incomplete reservoir distribution controlled by traps [1–7] The Fuyu oil layer in the Sanzhao depression is located in the but also has the characteristics such as the reservoir pressure northern Songliao Basin, which is close to the source rock of different from the characteristics of in-source tight oil [8]. the Qingshankou Formation, and its own reservoir is rela- The Fuyu oil layer has experienced many years of continuous tively tight. Therefore, it has become typical tight oil under exploration and practice, and predecessors have done a lot of source in China. The Fuyu oil layer not only has some typical research on its source rock conditions, sedimentary environ- characteristics of tight oil within the source, such as poor ment, preservation conditions, and other petroleum geologi- reservoir physical properties, large distribution area, low cal conditions [9–12], which has been clear that it has a Downloaded from http://pubs.geoscienceworld.org/gsa/lithosphere/article-pdf/doi/10.2113/2021/2609923/5362829/2609923.pdf by guest on 28 September 2021 2 Lithosphere 0 1020304050km Crataceous Formation Period Bed thickness (m) Source bed Reservoir Cover coat Stratigraphic section Seismic reflection interface Heiyupao depression Oil layer name Second Wuyuer depression 0–381 Mingshui Chronostratigraphy K2m Mingshui terrace First 0–243 Suiling anticline Taikang upli belt 0–413 Sifangtai K2s T03 Fih 0–355 T04 Fourth 0–290 Heidimiao Nengjiang Suihua depression K2n H ird 50–117 T06 Second e overlap belt of the west 80–253 T 86.68±0.47 Ma First 27–222 07 Changyuan anticline Hulan upli belt T S Saertu Second 50–150 1 Yaojia K2y Sanzhao depression First 10–80 T 1 P Putaohua ird 1 88.0±0.3 Ma Chaoxanggou terrace 53–552 Qingshankou G Gaotaizi K2qn Second 90.4±0.44 Ma Longhupaodaan terrace Upper cretaceous Upper First 25–164 T 91.3±0.48 Ma Qijiagulong depression Wangfu depression 2 Fourth 0–128 F Fuyu ird 0–692 Yangdachengzi Primary Y sructural belt 1 Changchunling anticline Secondary T2 sructural belt Quantou K2q Proven oil reserves Second 0–479 Proven gas reserves Forecast oil reserves Qingshankou anticline Controlled First 0–855 Changling depression Fuxin upli belt oil reserves T3 (a) (b) Figure 1: Exploration situation map and stratigraphic comprehensive column of the northern Songliao Basin. potential scale of tight oil resources of nearly two billion tons, when the Fuyang oil layer was developed, the Sanzhao but there is still a lack of in-depth discussion and research on depression has the sedimentary characteristics of multiple the relationship between the evolution of the reservoir and sources and multiple water catchment centers. As a whole, the process of accumulation. From the perspective of tight it was dominated by delta front and plain deposits. The river oil, the relative sequence between the densification time of is small in scale and changeable in direction, with the average the reservoir and the main accumulation period directly width being generally less than 800 meters, the thickness of affects the oil and gas abundance and enrichment zones of the sand body is thin, and the average thickness of a single the Fuyu oil layer. If the reservoir is tight first and then accu- sand body is generally less than 4 meters. The overlying mulates, then for the already densified reservoir, the reservoir Qing 1st member source rock has a relatively high abun- has basically lost its ability to transport oil and gas, and under dance of organic matter, mainly type I kerogen, with an the control of the fault-dominated transport system, explora- average organic carbon of 3.14% and the average of chloro- tion should be given priority to high-quality sweet spots near form bitumen A of 0.62%. The average of total hydrocar- faults. On the contrary, exploration can be carried out in bons is up to 4290 × 10−6 ppm, and the average value of areas rich in sand bodies with far faults. Therefore, research the sum of S1 and S2 is as high as 29.27 mg/g. Under the on the reservoir densification and accumulation process is influence of compression and overturning of multiple tec- of great practical significance for releasing tight oil resources tonic stresses, the top surface of the Quantou Formation in the Songliao Basin and further realizing the potential of has a complex structure with alternating uplifts and depres- tight oil. sions and developed nearly 4000 dense faults; the average length is less than 2 km, the vertical fault distance is distrib- 2. Geological Background uted in 20 to 60 meter, and the direction is mainly north- north-west and north-north-east. Exploration practice has The Songliao Basin is a large-scale Mesozoic-Cenozoic com- confirmed that the Fuyang oil layer has relatively poor posite sedimentary basin with a faulted depression double physical properties, with porosity generally ranging from structure, which has developed the Sanzhao depression, 8% to 12% and permeability ranging from 0.2 to 1.2 mD, Qijia-Gulong depression, Heiyupao depression, Changyuan which was dominated by fault-lithologic reservoirs. In the anticline, Mingshui terrace, Chaoyanggou anticline, and past three years, nearly 150 million tons of tight oil reserves other multiple tectonic units. The Sanzhao depression is have been submitted, demonstrating good exploration located in the middle-eastern part of the Songliao Basin, potential. and the middle-shallow exploration strata above 2000 meters are developed with the Fuyang oil layer (FY), Gaotaizi oil layer 3. Lithological Features of the Reservoir (G), Putaohua oil layer (P), Saertu oil layer (S), and other sets of oil-bearing layers from bottom to top, and the main source 3.1. Rock Types and Composition Characteristics. The lithol- rock is the high-quality dark rock of the Qingshankou For- ogy of the Fuyu oil layer mainly includes fine sandstone, fi fi mation (K2qn). The structural diagram of the Songliao Basin siltstone, silt-bearing ne sandstone, rare medium- ne sand- is shown in Figure 1. During the Quantou Formation period stone, and medium sandstone. The rock types are mainly Downloaded from http://pubs.geoscienceworld.org/gsa/lithosphere/article-pdf/doi/10.2113/2021/2609923/5362829/2609923.pdf by guest on 28 September 2021 Lithosphere 3 200 �m 100 �m (a) (b) 200 �m 200 �m (c) (d) Figure 2: Particle contact relation of the compact reservoir in the Fuyu Formation: (a) Shuang 51, the casting thin sections, 1724.09 m, plane- polarized light, ×100; (b) Fang 51, the casting thin sections, 1888.57 m, orthogonal light, ×200; (c) Fang 50, the casting thin sections, 1810.22 m, orthogonal light, ×100; (d) Zhao 26, the casting thin sections, 1886.86 m, orthogonal light, ×100. feldspar lithic sandstone and lithic feldspar sandstone. Quartz 4. Reservoir Diagenesis and content distribution is in the range of 16.06% to 64.29%, with Diagenetic Sequence an average of 28.2%, and feldspar content ranges from 16.28% to 53.45%, with an average of 34.22%.