Qijia Area Research Articles

Geological characteristics of unconventional tight oil reservoir (109 t): A case study of Upper Cretaceous Qingshankou Formation, northern Songliao Basin, NE China

The Daqing exploration area in the northern Songliao Basin has great potential for unconventional oil and gas resources, among which the total resources of tight oil alone exceed 109 t and is regarded as an important resource base of Daqing oilfield. After years of exploration in the Qijia area, Songliao Basin, NE China, tight oil has been found in the Upper Cretaceous Qingshankou Formation. To work out tight oil’s geological characteristics, taking tight oil in Gaotaizi oil layers of the Upper Cretaceous Qingshankou Formation in northern Songliao Basin as an example, this paper systematically analyzed the geological characteristics of unconventional tight oil in Gao3 and Gao4 layers of the Qijia area, based on the data of the geological survey, well drilling journey, well logging, and test. It is that three sets of hydrocarbon source rocks (K2qn1, K2qn2+3, and K2n1) develop in the examined area, and exhibit excellent type I and II kerogens, high organic matter abundance, and moderate maturity. The reservoir is generally composed of thin-bedded mudstone, siltstone, and sandstone, and presents poor porosity (average 8.5 vol.%) and air permeability (average 4 mD). The main reservoir space primarily includes intergranular pores, secondary soluble pores, and intergranular soluble pores. Three types of orifice throats were identified, namely fine throat, extra-fine throat, and micro-fine throat. The siltstone is generally oil-bearing, the reservoirs with slime and calcium become worse oil-bearing, and the mudstone has no obvious oil-bearing characteristics. The brittleness indices of the sandstone in the tight oil reservoir range from 40% to 60%, and those of the mudstone range from 40% to 45%, indicating a better brittleness of the tight oil reservoir. Based on the study of typical core hole data, this paper gives a comprehensive evaluation of the properties of the tight oil and establishes a tight oil single well composite bar chart as well as the initial evaluation system with the core of properties in the tight oil reservoir. This study has theoretical guiding significance and practical application value for tight oil exploration and evaluation in the Qijia area.©2024 China Geology Editorial Office.

Reservoir properties and genesis of tight sandstones—A case study from the Gaotaizi oil layer in the Qijia area, Songliao basin

The primary focus of oil and gas exploration for tight sandstone reservoirs is on a quantitative characterization of reservoir properties. This paper uses the tight sandstone reservoir developed in the Gaotaizi oil layer in the Qijia area of the Songliao Basin as an example. The petrology, physical properties, pore–throat characteristics, and the genesis of the densification of the oil-bearing sandstones are elucidated using casting thin-sections, scanning electron microscopy, 3D computerized tomography (CT), and petrophysical experimental techniques. The results show that the Gaotaizi oil layer is mainly composed of clastic rocks and contains small amounts of shell limestone. The clastic rocks are mainly lithic feldspar sandstone and feldspar lithic sandstone, while residual intergranular pores, intergranular dissolved pores, intragranular dissolved pores, intragranular pores and intercrystalline pores constitute the different pore types. Mercury intrusion and 3D computerized tomography analysis showed that micro-nano pores account for 53% of the total pores present. The pore–throat coordination number is distributed between 1 and 4, with an average of 1.8. The pores and throats in the Gaotaizi reservoir have poor connectivity. The porosity distribution of the Gaotaizi oil layer is 1.4%–22.5%, with an average of 9.5%, while the permeability distribution ranges from 0.01 to 27.10 mD, with an average of 0.41 mD. It is an ultra-low porosity and ultra-low permeability tight reservoir. The Gaotaizi oil layer is divided into three types of reservoirs through a systematic study of its pore developmental characteristics. Diagenetic processes like compaction and cementation result in a reduction in porosity and permeability. Compaction, calcite and siliceous cementation, and illite packing are primarily responsible for reservoir densification.

Study of the lower limit of pore throat filling in tight sandstone reservoir of Gaotaizi oil layer in Qijia area

The study of the lower limit of filling of the pore throat in tight sandstone reservoirs is an essential part of reservoir evaluation. It can guide exploration and development and helps understand tight oil accumulation and estimate saturation. Determining this lower limit of pore throat filling has mainly been based on experience in a particular reservoir or field, and there is a lack of theoretical and experimental support. In this paper, the lower limit of pore throat filling of the tight sandstone reservoir in the Gaotaizi oil layer in the Zijia area is theoretically derived. Experiments show that oil charging at the source-reservoir interface is affected by the increasing pressure within the reservoir due to hydrocarbon generation. Based on the equilibrium relationship between the hydrodynamic effects and the actual reservoir parameters, the theoretical derivation of the lower limit of the pore throat diameter at the source-reservoir interface is 23.6 nm. The mechanical mechanism of the internal charging of the reservoir is different from the source-reservoir interface. In this paper, the lower limit of the pore throat filling in the Gaotaizi reservoir is 54.45 nm based on environmental scanning electron miscopy and the energy spectrum. Combined with the analysis of mercury injection tests, the lower limit of the filling pore throat is used to determine that oil saturation near the source-reservoir interface is 33%, and 19% within the reservoir. The results of the study on the lower limit of pore throat filling in different parts of the reservoir provide a theoretical basis and prediction method for the distribution and target evaluation of tight oil sandstone.

Application of rock brittleness evaluation in tight oil exploration—— Taking Lijiaweizi Fault Depression in Qijia Area as an Example

Brittle rock is one of the key factors in the use of unconventional oil and gas exploration technology to be considered, The stronger the brittleness of rock is, the easier to produce fractures to form fracture network in the over flushing of fracturing, the stock of oil and gas storage layer will be increased, and the production of single well will be increased. At present mainly based on rock elastic parameters, we use Young’s modulus and Poisson’s ratio of two ways to analyze brittle rock in earthquake prediction evaluation. However, since these two methods in the process, both the need for elastic parameters of rock normalized, leading to large errors, adaptability reduce. Based on this, we propose a Young’s modulus and Poisson’s ratio coefficient of utilization of compared to the brittle rock evaluation method to effectively improve the accuracy of prediction and evaluation of brittle rock and anti-jamming capability, while the brittle evaluation method based on the use of pre-stack seismic inversion of elastic parameters to Qijia area of Songliao basin compact oil brittle rock predict deployment guidance wells to obtain stable high level of industrial oil flow.

Detailed characterization of micronano pore structure of tight sandstone reservoir space in three dimensional space: a case study of the Gao 3 and Gao 4 members of Gaotaizi reservoir in the Qijia area of the Songliao basin

Tight sandstone samples from the Gao 3 and Gao 4 members of Gaotaizi reservoir in Qijia area of the northern Songliao Basin were targeted as the main research objects in this paper. Through micro/nano CT technology and auto skeleton module and connectivity module in avizo software, three-dimensional models for the micro pore structure of Gaotaizi tight sandstone in the research area were constructed. The experimental results demonstrate that types of reservoir space include intergranular dissolution pores, intragranular dissolution pores, and micro-fractures, indicating remarkable microscopic heterogeneity with characteristics of a continuous distribution in a micronano scale. Under the micro scale, different physical property and sedimentary microfacies of tight reservoir show various pore structure characteristics in three-dimensional space, with the primary front of pore throats mainly distributed in 0.6~1.5 μm. Under the nanoscale, micro heterogeneity is remarkable, with the primary front of pore throats distributed in 40~100 nm. In addition, the nanopore distribution pattern in three-dimensional space mainly includes the nanopores in the granules and the nanofractures, of which the latter type plays a crucial role in connecting nanopores and migration of nano oil and gas migration; at the same time, this paper verify the digital core experimental results by using MICP technology. With the further development of big data technology and deep learning technology, three-dimensional digital core technology based on micro/nano CT technology will become an important technology applied in the exploration and development of unconventional oil and gas.

Grading evaluation of pore throats in a tight sandstone reservoir: a case study of the Gao 3 section reservoir in the Qijia area of the Songliao Basin

The micropore throat of the Gao 3 section tight sandstone reservoir was studied using sampling and experimental (high-pressure mercury injection and scanning electron microscopy) methods. Based on the relative permeability, the reservoir can be divided into three categories: conventional, unconventional and low permeability. To determine the displacement pressure, porosity and other relevant parameters of various reservoirs, the mercury injection curve of all samples was projected to the same coordinate system. According to the position of the inflection point on the mercury injection curve of all levels of reservoirs, the pore throat was divided into three types: micropores, transition pores and macropores. Based on the theory that the throat is characterised by the mercury withdrawal curve, the throat in the present study is divided into three categories: the large throat, the medium throat and the small throat. Combined with the ordinate position at the inflection point, the critical point of micropore-throat classification of all kinds of reservoirs was determined. By analysing the histogram of pore-throat distribution of all kinds of reservoirs, the peak value of reservoir pore-throat distribution was determined. From the definition of expectation and variance in mathematics, the concept of grading parameters was introduced to determine the size and concentration degree of micropore-throat distribution at all levels of reservoirs, and a correlation analysis with permeability was performed to determine the control law of permeability.

Control function of Sedimentary Facies on Tight Oil Distribution—Taking Gaotaizi Oil Layer in Qijia Area as An Example

In order to find out the controlling factors of tight oil distribution in Gaotaizi oil layer, Qijia area, the authors consider that the sediment facies is shallow delta in G3-G4 oil layer through the fine study of sedimentary characteristics, and develops delta plain, delta front and prodelta subfacies from north to south. Multiple and small scale transgressions during with the base level falling cause the multistage superposition between delta outer front with prodelta mud, and the terminal of delta inner front with the mud of delta outer front, which provide the premise of source and storage match for inner source tight oil. Then, the authors analyze the control action of sediment facies on tight reservoir, high quality oil layers and the matching relationship between them, and point that there exist two kinds of tight oil reservoir in Qijia area, tight reservoir of distal bar in the rear of delta inner front, tight reservoir of sheet sand in delta outer front. By comparing the superiority of the three conditions, the former is better in reservoir condition, hydrocarbon source rock condition and source storage matching, which is the most important tight oil reservoir type. Finally, it is pointed out the tight reservoir of distal bar in rear of delta outer front is the most favorable microfacies in the next tight oil exploration in southern Qijia area.

松辽盆地齐家北地区扶余油层FI1油层组沉积相及有利区预测

松辽盆地齐家北地区扶余油层FI1油层组沉积相及有利区预测

Determination of accumulation periods and relative maturity of tight oil and gas in Gaotaizi oil reservoir of Qijia area by using fluorescence spectrum of oil inclusions

Determination of accumulation periods and relative maturity of tight oil and gas in Gaotaizi oil reservoir of Qijia area by using fluorescence spectrum of oil inclusions

The tight reservoir microscopic classification of southern part of Qijia area in Songliao Basin

With the decreasing of the conventional oil and gas reserves, the unconventional tight oil and gas are gradually becoming the focus of the study. The casting thin section, conventional mercury injection, constant velocity and pressure mercury and other experimental methods, tight reservoir microscopic characteristics in southern part of Qijia area were studied in this paper. Based on the above conditions, combined with the parameters of pore type, pore throat radius, the reservoir is divided into two types, conventional reservoir and low permeability tight reservoir. Reservoir conventional reservoir permeability values are greater than 1mD, low permeability tight reservoirs are classified into IIa type and IIb type, which provides some reference value for the actual exploration and development.

Analysis of Influencing Factors on Pore Structure of Gaotaizi Reservoir in QIJIA

The Qijia area is located in the Qijia-Gulong sag of Daqing Placanticline. The Gaotaizi oil reservoir is a compact muddy siltstone assemblage with four oil groups. The third and fourth high-formation groups are the main force Generating layer of the Qingshankou formation. The Gaotaizi oil layer is buried deep, and these layers are subject to strong diagenetic transformation. Based on the study of reservoir microstructural characteristics, the main control factors of reservoir pore structure are sedimentary, diagenesis and waterflooding development using core data, microscopic images and logging data. The controlling effect of different sedimentary microfacies on pore structure was studied through studying the characteristics of sedimentary microfacies type in the study area. The controlling effect of diagenesis on pore structure was studied through the diagenetic evolution characteristics.The controlling effect of waterflooding on pore structure was studied by observing microcosmic characteristics of reservoirs with different washing degree.

Sedimentary characteristics and seismic geomorphologic responses of a shallow-water delta in the Qingshankou Formation from the Songliao Basin, China

With the aid of modern sedimentology, seismic geomorphology, and the comprehensive analysis of geophysical data and core data from more than 10 wells, the Qingshankou Formation has been divided into 3 long-term cycles and further into 6 medium-term cycles in the Qijia area, Songliao Basin. The 3 long-term cycles, SQ1, SQ2 and SQ3 correspond to the members Qing I, Qing II and Qing III of the Qingshankou Formation, spanning 11.5 Ma during the Late Cretaceous. The time scale of the medium-term cycles, which are subunits of the long-term cycles, is approximately 0.5–1.5 Ma with thicknesses ranging from 45 m to 116 m. A shallow-water delta that consists of high-maturity fine-grained sandstone developed in the Qingshankou Formation. The scour surfaces reflect strong flow action, and the parallel bedding and large-scale cross bedding are well developed. Distributary channel sandstones are well developed in the shallow-water delta depositional system, in which a single channel can be several meters thick. The cumulative thickness of the distributary channels can reach tens of meters across a large area, extending tens of kilometers to the center of the lacustrine basin. The development of the subaqueous distributary channel of the shallow-water delta is closely related to base level (lake level) changes. In the early stage of a rising half-cycle and the late stage of a falling half-cycle, the fluviation is significant and the well-developed channel sandstone can extend towards the center of the lacustrine basin more than 50 km, with large cumulative thicknesses of compound sandbodies (17–28 m) and high sandstone-to-strata ratios (78–88%). In the late stage of a rising half-cycle and the early stage of a falling half-cycle, the lake level is high and the fluviation is weak, resulting in a distributary channel extent of less than 30 km, small cumulative thicknesses of compound sandbodies (5–12 m) and low sandstone-to-strata ratios (22–45%). The delta front can be divided into the inner front and the outer front. The subaqueous distributary channels in the inner front have good continuity and extend further, whereas the subaqueous distributary channels in the outer front have poor continuity, and sheet sand is well developed. Therefore, a shallow-water delta generally shows features including (1) sedimentary structures formed by strong currents, (2) stacked fining upward rhythm, (3) subaqueous distributary channels well developed, (4) delta front divided further into an inner and an outer front. There was a relatively good linear relationship between the thickness of the sandbody based on the well data and the maximum amplitude of the seismic trace next to the well. The reddish amplitude of the seismic attribution suggests thicker channel sandbodies (4–9 m), whereas the light amplitude of the seismic attribution indicates thinner channel sandbody (1–4 m). Of the two typical sedimentary models for shallow-water deltas, delta plains develop well in humid climates and delta fronts develop well in arid climates, both of which are found in the Qijia area, Songliao Basin. Stratal slices from seismic geomorphology are applied to display the branchlike sandstone dispersal patterns of the shallow-water delta and the broad distribution characteristics. This study also notes that the delta front distributary channel sandstone, which is near an oil source and faults, would be a favorable exploration target.

Distribution and formation of tight oil in Qijia area, Songliao Basin, NE China

Abstract By using geologic, geochemical, well test, well drilling and well logging data, the formation conditions and distribution pattern of tight oil in Gao 3 and Gao 4 oil layers of Gaotaizi layer, Upper Cretaceous Qingshankou Formation, Qijia area, Songliao Basin were examined systematically. There are four favorable conditions for the formation of tight oil: high quality source rocks and reservoirs, good source and reservoir combination, and formation pressure. There are three series of source rocks in this area, K2qn1, K2qn2+3 and K2n1, which provided material basis for the tight oil reservoirs; reservoirs including a variety of sands like distributaries channel, mouth bar and sheet sand are large in total thickness, wide in lateral distribution and good in continuity, providing accumulation space for tight oil; reservoir rocks of delta front in direct contact with the hydrocarbon source rock or pinching out in hydrocarbon source rock like fingers or interbedded with hydrocarbon source rock, constituted good source-reservoir combinations; abnormal overpressure in tight oil reservoirs with the pressure factor of 1.2-1.5, provided drive force for tight oil migration and charging. The study shows tight oil of Gao 3 and Gao 4 oil layers in Qijia area is mainly distributed in the center of, and slope and terrace around the sag.

A Study of Identification Marks of Sequence Boundary of GaoTaizi Reservoir in Qijia Area

According to the high resolution sequence stratigraphy’s theory[1] and the information of rock-mineral analysis, geophysics data, biological stratigraphy and geochemistry, this paper made a systematical and in-depth research on sequence boundary identification marks of Gaotaizi reservoir of Qijia area in songliao basin. We use core identification, logging curve, paleontology, heavy mineral analysis and seismic prospecting data to explain how to find the sequence boundary. And there are two types of boundary were recognised on G3,G4 oil layer group of Qijia area, which are used to be the basis to make G3,G4 into 5 parts, one is the transition surface of deltaic plain and shallow lake, the other is the top of ascending order of delta front.

Seismic prediction of sandstone diagenetic facies: Applied to Cretaceous Qingshankou Formation in Qijia Depression, Songliao Basin, East China

Abstract Seismic diagenetic facies is an important control on reservoir quality. This study investigated the feasibility of predicting sandstone diagenetic facies using conventional 3D seismic data by seismic sedimentology and calibrated by laboratory core-analysis data in the Qijia area of the Songliao Basin. Three core issues are related to seismic characterization of diagenetic facies, including how to correlate stratigraphic and diagenetic units from seismic data, how to evaluate the relationship between core-based diagenetic facies and seismic attributes, and how to find an effective way of mapping seismic diagenetic facies. Well- and seismic-based, high-resolution sequence analysis and seismic stratal slicing provide reservoir-scale (20 m) seismic representations of diagenetic units. Core-based analyses of sandstone diagenetic processes and diagenetic sequences reveal the kind of diagenesis that most influences reservoir quality. An investigation of reservoir parameters and acoustic rock properties further reveals the link between diagenetic facies and impedance, leading to a recognition of calcite cementation as the process that can be detected by seismic data. A seismic-based lithology cube (e.g., 90°-phased seismic volume) provides the amplitude (impedance) signal for detection of diagenetic facies. Stratal slices made from the seismic-based lithology cube are then used to interpret depositional facies and systems. Eventually a seismic diagenetic-facies map is generated through analysis of the relationships between depositional facies, impedance, and diagenetic facies. A case study of clay- and calcite-cemented sandstone in the Qijia area shows that although still in its infancy, seismic detection of sandstone diagenetic facies using conventional seismic data is definitely feasible.

Guidelines for seismic sedimentologic study in non-marine postrift basins

Abstract This study summarizes the research experiences of non-marine seismic sedimentology in recent years in China and uses Qijia area, Songliao Basin, as a template to establish general guidelines for seismic sedimentology. Basic data sets include stacked 3D seismic volumes, 2D regional seismic lines, data for regional geologic settings, and well data. The workflow emphasizes the integration of seismic and geologic interpretations and balanced use of seismic sedimentology, sequence stratigraphy and seismic stratigraphy. Basic steps include well-to-seismic tie for the establishment of sequence framework, wavelet-phase adjustment, picking of geologic-time parallel seismic events, seismic resolution analysis, petrophysical analysis, selection of seismic attributes, stratal slicing, seismic depositional facies analysis, and applications to exploration and development. Expected maps range from key interpreted well-seismic sections, flattened relative geologic-time sections, stratal slices, and depositional facies maps, etc. The workflow is applied in the study of the Cretaceous Qingshankou Formation in the Qijia area, Songliao Basin, which can be used as a reference for seismic sedimentologic study in non-marine basins, especially in postrift depression-type basins in China.