scholarly journals Reservoir characteristics and control mechanism of resistivity low-contrast oil pays in Chang 8 tight sandstone of Longdong West area, Ordos Basin

2021 ◽  
Author(s):  
Ze Bai ◽  
Maojin Tan ◽  
Yujiang Shi ◽  
Gaoren Li ◽  
Simon Martin Clark
Keyword(s):  
Control Mechanism ◽  
Ordos Basin ◽  
Water Salinity ◽  
Formation Water ◽  
Tight Sandstone ◽  
Low Contrast ◽  
Reservoir Characteristics ◽  
The Difference ◽  
Formation Water Salinity ◽  
And Control

AbstractLog interpretation and evaluation of tight sandstone reservoir in Chang 8 Member of Longdong West area, Ordos Basin, China, are facing great challenges due to the co-development of normal oil pay and resistivity low-contrast oil pay. To better guide the exploration and development of oil resources in this area, the reservoir characteristics and control mechanism of resistivity low-contrast oil pay were studied. Firstly, the reservoirs were divided into resistivity low-contrast oil pay (RLP) and normal oil pay (NP) based on the relative value of the apparent resistivity increase rate. Then, the difference of reservoir characteristics between RLP and NP is analyzed by comparing a series of experimental data and real logging data in those two reservoir types. Finally, the control mechanism of RLP was studied from reservoir micro-factors and regional macro-factors, respectively. It is found that the chlorite and illite are the most abundant clay minerals in RLP and NP, respectively. Compared with NP reservoir, the average porosity of RLP is better, but the pore space is mainly composed of micropores, which lead to smaller average pore throat radius and poor pore structure. The high irreducible water saturation and high formation water salinity reduced the reservoir resistivity from micro-aspect. Besides, the difference of hydrocarbon expulsion capacity of source rock and the regional difference of formation water salinity controlled the distribution of RLP and NP. Comprehensive consideration of the reservoir micro-factors and regional macro-factors is important to carry out effective logging interpretation and evaluation.

scholarly journals Using the Modified Resistivity–Porosity Cross Plot Method to Identify Formation Fluid Types in Tight Sandstone with Variable Water Salinity

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6335
Author(s):  
Yufei Yang ◽  
Kesai Li ◽  
Yuanyuan Wang ◽  
Hucheng Deng ◽  
Jianhua He ◽  
...  
Keyword(s):  
Water Saturation ◽  
Ordos Basin ◽  
Water Layer ◽  
Water Salinity ◽  
Water Type ◽  
Formation Water ◽  
Tight Sandstone ◽  
Fluid Identification ◽  
Low Resistivity ◽  
Formation Water Salinity

It is generally difficult to identify fluid types in low-porosity and low-permeability reservoirs, and the Chang 8 Member in the Ordos Basin is a typical example. In the Chang 8 Member of Yanchang Formation in the Zhenyuan area of Ordos Basin, affected by lithology and physical properties, the resistivity of the oil layer and water layer are close, which brings great difficulties to fluid type identification. In this paper, we first analyzed the geological and petrophysical characteristics of the study area, and found that high clay content is one of the reasons for the low-resistivity oil pay layer. Then, the formation water types and characteristics of formation water salinity were studied. The water type was mainly CaCl2, and formation water salinity had a great difference in the study area ranging from 7510 ppm to 72,590 ppm, which is the main cause of the low-resistivity oil pay layer. According to the reservoir fluid logging response characteristics, the water saturation boundary of the oil layer, oil–water layer and water layer were determined to be 30%, 65% and 80%, respectively. We modified the traditional resistivity–porosity cross plot method based on Archie’s equations, and established three basic plates with variable formation water salinity, respectively. The above method was used to identify the fluid types of the reservoirs, and the application results indicate that the modified method agrees well with the perforation test data, which can effectively improve the accuracy of fluid identification. The accuracy of the plate is 88.1%. The findings of this study can help for a better understanding of fluid identification and formation evaluation.

Analysis of main controlling factors and identification method of Jurassic low resistivity reservoir in Huanxian area, Ordos Basin

2021 ◽  
Author(s):  
Jingzhe Guo ◽  
Lifa Zhou
Keyword(s):  
Apparent Resistivity ◽  
Ordos Basin ◽  
Controlling Factors ◽  
Water Salinity ◽  
Formation Water ◽  
Low Resistivity ◽  
Reservoir Fluid ◽  
Oil Resources ◽  
The Ordos Basin ◽  
Formation Water Salinity

<p>The Ordos Basin is located in the central and western part of China, which is rich in oil resources in Mesozoic strata. Huanxian area is located in the west of the Ordos Basin, covering an area of about 3000 km<sup>2</sup>. With the wide distribution of Jurassic low resistivity reservoir, it is difficult to identify reservoir fluid by logging, which restricts the efficient promotion of oil resources exploration and development in this area to a certain extent.</p><p>Based on the basic geological law, this study makes full use of the data of oil test conclusion, production performance and formation water analysis to deeply analyze the genesis of low resistivity reservoir in this area. The average formation water salinity of Jurassic in Huanxian area is 63.5g/l. Through the correlation analysis of mathematical methods such as fitting and regression, the formation water salinity and reservoir apparent resistivity show a good negative correlation in the semi logarithmic coordinate, and the correlation coefficient is 0.78. Therefore, it is considered that the main controlling factor for the widespread development of low resistivity reservoir in this area is the high formation water salinity. Irreducible water saturation, clay mineral content and nose bulge structure amplitude are the secondary controlling factors for the development of low resistivity reservoir in this area, and their correlation coefficients with apparent resistivity are 0.23, 0.25 and 0.31, respectively.</p><p>On the basis of clarifying the genesis of Jurassic low resistivity reservoir in Huanxian area, the comprehensive identification of reservoir fluid type by logging is carried out. For the whole area, there are obvious differences in geological characteristics, so conventional methods such as cross plot method of acoustic time difference and apparent resistivity can not effectively identify reservoir fluid. According to the main controlling factors of reservoir apparent resistivity, the salinity of formation water is combined with apparent resistivity and resistivity index of reservoir respectively to establish the cross plot. Using these two kinds of cross plot, the accuracy of reservoir fluid type identification is 62.9% and 88.6% respectively. This method can meet the accuracy requirements of reservoir fluid identification, realize the rapid identification of reservoir fluid types in the whole area, and provide technical support for efficient exploration and development of Jurassic low resistivity reservoir in this area.</p>

A NEUTRON-INDUCED GAMMA-RAY SPECTROSCOPY LOGGING METHOD FOR DETERMINING FORMATION WATER SALINITY

2019 ◽  
Author(s):  
Lili Tian ◽  
Feng Zhang ◽  
Quanying Zhang ◽  
Qian Chen ◽  
Xinguang Wang ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Water Salinity ◽  
Formation Water ◽  
Gamma Ray Spectroscopy ◽  
Formation Water Salinity

scholarly journals Thermal Stability and Compatibility of Surfactants in Presence of Formation Water Salinity under Reservoir Conditions

2020 ◽  
Vol 39 (4) ◽  
pp. 826-830
Author(s):  
Muhammad Khan Memon ◽  
Ubedullah Ansari ◽  
Habib U Zaman Memon
Keyword(s):  
Thermal Stability ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Gas Injection ◽  
Surfactant Solution ◽  
Water Salinity ◽  
Formation Water ◽  
Reservoir Temperature ◽  
Gas Mobility ◽  
Formation Water Salinity

In the surfactant alternating gas injection, the injected surfactant slug is remained several days under reservoir temperature and salinity conditions. As reservoir temperature is always greater than surface temperature. Therefore, thermal stability of selected surfactants use in the oil industry is almost important for achieving their long-term efficiency. The study deals with the screening of individual and blended surfactants for the applications of enhanced oil recovery that control the gas mobility during the surfactant alternating gas injection. The objective is to check the surfactant compatibility in the presence of formation water under reservoir temperature of 90oC and 120oC. The effects of temperature and salinity on used surfactant solutions were investigated. Anionic surfactant Alpha Olefin Sulfonate (AOSC14-16) and Internal Olefin Sulfonate (IOSC15-18) were selected as primary surfactants. Thermal stability test of AOSC14-16 with different formation water salinity was tested at 90oC and 120oC. Experimental result shows that, no precipitation was observed by surfactant AOSC14-16 when tested with different salinity at 90oC and 120oC. Addition of amphoteric surfactant Lauramidopropylamide Oxide (LMDO) with AOSC14-16 improves the stability in the high percentage of salinity at same temperature, whereas, the surfactant blend of IOSC15-18 and Alcohol Aloxy Sulphate (AAS) was resulted unstable. The solubility and chemical stability at high temperature and high salinity condition is improved by the blend of AOSC14-16+LMDO surfactant solution. This blend of surfactant solution will help for generating stable foam for gas mobility control in the methods of chemical Enhanced Oil Recovery (EOR).

RELATIONSHIP BETWEEN FORMATION WATER SALINITY AND BIOGENIC COALBED METHANE: BLACK WARRIOR BASIN, ALABAMA (USA)

2016 ◽  
Author(s):  
Tyler Gilkerson ◽  
◽  
Jack C. Pashin ◽  
Tracy M. Quan ◽  
Thomas H. Darrah ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Water Salinity ◽  
Formation Water ◽  
Black Warrior Basin ◽  
Formation Water Salinity

Source and reservoir characteristics of Upper Triassic lacustrine Chang 6 tight oil play in Zhangjiagou area, Ordos Basin, China

2021 ◽  
pp. 1-27
Author(s):  
Yan Cao ◽  
Hui Han ◽  
Shijia Chen ◽  
Rui Liu ◽  
Jingyue Zhang ◽  
...  
Keyword(s):  
Upper Cretaceous ◽  
Ordos Basin ◽  
Micropore Volume ◽  
Source Rocks ◽  
Gas Chromatography Mass Spectrometry ◽  
Major Type ◽  
Tight Oil ◽  
Tight Sandstone ◽  
Yanchang Formation ◽  
Reservoir Characteristics

To explore the source and reservoir characteristics of Chang 6 tight oil in the Zhangjiagou area, we have extracted a suite of Chang 6 tight sandstones and the source rocks from the seventh to ninth members of the Upper Cretaceous Yanchang Formation in the Ordos Basin, China, respectively, using chloroform. We examined group components by fractionations of extracted organic matter. Using low-pressure gas adsorptions and gas chromatography-mass spectrometry, respectively, we analyzed the pore structure of the studied samples before and after extraction and the oil source of the separate saturated hydrocarbon components. The results indicate that the porosity of the Chang 6 tight sandstone is mainly distributed in the 8%–14% range, averaging 10.5%, the permeability of the studied reservoir is only approximately 0.16 × 10−3 μm2, and the pore-throat radius is mainly less than 2 μm. The major type of pores of the reservoir includes the residual intergranular pore, secondary intergranular dissolved pore, and intragranular dissolved pore. The micropore volume of the Chang 6 tight sandstone is in the range of 0.0071–0.0092 cm3/g, and the mesopore volume of the Chang 6 tight sandstone is in the range of 0.0237–0.0343 cm3/g. The micropore volume and micropore surface area significantly increased after chloroform extractions, and soluble hydrocarbons could be stored in micropores of the Chang 6 tight sandstone. The three sets of source rocks from the seventh to ninth members of the Upper Cretaceous Yanchang Formation are high quality by the evaluation of source rocks, and the Chang 7 has the highest value of source rocks, followed by Chang 9 and Chang 8. The pentacyclic triterpene characteristics (Ts-C30H-C30*) of Chang 6 crude oil are similar to those of Chang 7 source rock, and the tight oil of the Chang 6 member in the Zhangjiagou area originated from Chang 7 source rocks.

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