mercury injection
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2021 ◽  
Author(s):  
Zhongxia Li ◽  
Junwei Wan ◽  
Tao Xiong ◽  
Hongbin Zhan ◽  
Linqing He ◽  
...  

Abstract. This study provides experimental evidence of Forchheimer flow and transition between different flow regimes from the perspective of pore size of permeable stone. We have firstly carried out the seepage experiments of permeable stones with four different mesh sizes, including 24 mesh size, 46 mesh size, 60 mesh size, and 80 mesh size, which corresponding to mean particle sizes (50 % by weight) of 0.71 mm, 0.36 mm, 0.25 mm, and 0.18 mm. The seepage experiments show that obvious deviation from Darcian flow regime is visible. In addition, the critical specific discharge corresponding to the transition of flow regimes (from pre-Darcian to post-Darcian) increases with the increase of particle sizes. When the “pseudo” hydraulic conductivity (K) (which is computed by the ratio of specific discharge and the hydraulic gradient) increases with the increase of specific discharge (q), the flow regime is denoted as the pre-Darcian flow. After the specific discharge increases to a certain value, the “pseudo” hydraulic conductivity begins to decrease, and this regime is called the post-Darcian flow. In addition, we use the mercury injection experiment to measure the pore size distribution of four permeable stones with different particle sizes, and the mercury injection curve is divided into three stages. The beginning and end segments of the mercury injection curve are very gentle with relatively small slopes, while the intermediate mercury injection curve is steep, indicating that the pore size in permeable stones is relatively uniform. The porosity decreases as the mean particle sizes increases, and the mean pore size can faithfully reflect the influence of particle diameter, sorting degree and arrangement mode of porous medium on seepage parameters. This study shows that the size of pores is an essential factor for determining the flow regimes. In addition, the Forchheimer coefficients are also discussed in which the coefficient A (which is related to the linear term of the Forchheimer equation) is linearly related to 1/d 2 as A = 0.0025 (1/d 2) + 0.003; while the coefficient B (which is related to the quadratic term of the Forchheimer equation) is a quadratic function of 1/d as B =1.14E-06 (1/d)2 − 1.26E-06 (1/d). The porosity (n) can be used to reveal the effect of sorting degree and arrangement on seepage coefficient. The larger porosity leads to smaller coefficients A and B under the condition of the same particle size.


2021 ◽  
pp. 1-20
Author(s):  
A. A. Kasha ◽  
A. Sakhaee-Pour ◽  
I. A. Hussein

Summary Capillary pressure plays an essential role in controlling multiphase flow in porous media and is often difficult to be estimated at subsurface conditions. The Leverett capillary pressure function J provides a convenient tool to address this shortcoming; however, its performance remains poor where there is a large scatter in the scaled data. Our aim, therefore, was to reduce the gaps between J curves and to develop a method that allows accurate scaling of capillary pressure. We developed two mathematical expressions based on permeability and porosity values of 214 rock samples taken from North America and the Middle East. Using the values as grouping features, we used pattern-recognition algorithms in machine learning to cluster the original data into different groups. In each wetting phase saturation, we were able to quantify the gaps between the J curves by determining the ratio of the maximum J to the minimum J. Graphical maps were developed to identify the corresponding group for a new rock sample after which the capillary pressure is estimated using the average J curve of the identified group and the permeability and porosity values of the rock sample. This method also provides better performance than the flow zone indicator (FZI) approach. The proposed technique was validated on six rock types and has successfully generated average capillary pressure curves that capture the trends and values of the experimentally measured data by mercury injection. Moreover, the proposed methodology in this study provides an advanced and a machine-learning-oriented approach for rock typing. In this paper, we provide a reliable and easy-to-use method for capillary pressure estimation in the absence of experimentally measured data by mercury injection.


Nafta-Gaz ◽  
2021 ◽  
Vol 77 (10) ◽  
pp. 633-640
Author(s):  
Lidia Dudek ◽  
◽  
Konrad Ziemianin ◽  

Celem pracy było scharakteryzowanie przestrzeni porowej łupków menilitowych występujących w odsłonięciach powierzchniowych z rejonu Birczy w jednostce skolskiej. Wszystkie próbki zostały pobrane z całego profilu stratygraficznego w jednym odsłonięciu w Birczy o długości 1 m. Struktura porowa próbek łupków wygrzanych w 105°C była mierzona metodą porozymetrii rtęciowej (ang. mercury injection capillary pressure, MICP) w temperaturze otoczenia oraz metodą adsorpcji azotu w temperaturze wrzenia ciekłego azotu. Ze względu na deformację przestrzeni porowej pod wpływem wysokich ciśnień roboczych rtęci, z krokami ciśnienia od 0 do 4136,84 bara, mikropory i mezopory można błędnie interpretować. Jako metodę uzupełniającą zastosowano więc pomiar adsorpcji azotu w celu prawidłowego obliczenia całkowitej połączonej objętości porowej. Na wykresach dV/dD (pochodnych objętości względem średnicy) połączono wyniki z obu technik pomiarowych, uzyskując pełniejszy obraz rozkładu objętości porów. W pracy przedstawiono możliwość dokładniejszego obliczenia objętości porów na podstawie nowego podejścia do analizy wykresów pochodnych. Obie metody zapewniają również kompleksową ocenę parametrów struktury porów, w tym powierzchni właściwej (ang. specific surface area, SSA), objętości mikro- i mezoporów oraz rozszerzonego zakresu rozkładu wielkości porów (ang. pore size distribution, PSD). Porównując wyniki metody adsorpcyjnej z użyciem azotu z wynikami porozymetrii rtęciowej, należy pamiętać o różnicach w zakresach obu technik badawczych oraz o tym, że azot i rtęć rejestrują struktury porowe w znacząco odmienny sposób. Zatłaczanie rtęci do struktury porowej jest regulowane przez przewężenia porów, podczas gdy zjawisko adsorpcji jest kontrolowane przez powierzchnię porów. Zastosowanie porozymetrii rtęciowej i adsorpcji azotu do łupków menilitowych pokazuje, jak użycie tych dwóch metod może wpłynąć na uzyskanie wzajemnie uzupełniających się informacji, które weryfikują obliczenia objętości porowej głównej skały macierzystej dla karpackich rop naftowych.


2021 ◽  
Vol 9 ◽  
Author(s):  
Weiming Wang ◽  
Weihao La ◽  
Tanguang Fan ◽  
Xiongfei Xu ◽  
Yingnan Liu ◽  
...  

Self-jetting high-yield oil flow was obtained from Ma 67 and Ma 36 wells drilled in the volcanic reservoirs of the Haerjiawu Formation in the Santanghu Basin, China. This has shifted the prospectors’ attention to the Haerjiawu Formation from the Kalagang Formation, which is generally considered to have favorable physical properties. To further explain the geological reasons why oil flow can jet itself from the volcanic rocks in the Haerjiawu Formation with poor physical properties, this study carries out a systematic comparison on the microscopic pore structures of volcanic rocks through unconventional tests such as low-temperature nitrogen adsorption, high-pressure mercury injection, and constant-rate mercury injection based on the analyses of physical properties and minerals. The results obtained are as follows. The volcanic rocks of the Kalagang Formation have relatively high pore permeability. However, their micropores have a wide distribution range of pore size and feature highly meandering structures and strong heterogeneity. Meanwhile, small pore throats connect large pores in the volcanic rocks, resulting in a relatively high pore/throat ratio. All these are conducive to the occurrence of tight oil and gas but unfavorable for the flow of oil and gas. The volcanic rocks in the Haerjiawu Formation have relatively low volcanic permeability. However, small pores connect large pore throats in the volcanic rocks; thus, leading to a relatively low pore/throat ratio. Meanwhile, the volcanic rocks feature low meandering structures, strong homogeneity, and high connectivity. All these are favorable for the formation of tight oil and gas reservoirs. These assessment results also indicate that the assessment indices of tight volcanic reservoirs should not only include porosity and permeability. Instead, more attention should be paid to the microscopic pore structures, and it is necessary to analyze the charging and flow of tight oil from the configuration of pores and pore throats. This study not only explains the geological factors of the wells with self-jetting high-yield oil flow in the Haerjiawu Formation from the perspective of microscopic pore structures but also provides a new idea and comparison method for the assessment of tight reservoirs in other areas.


Author(s):  
Juan Alejandro Angel Restrepo ◽  
◽  
Ricardo Andrés Gómez-Moncada ◽  
Carlos Alberto Mora Sánchez ◽  
Ricardo Bueno Silva ◽  
...  

The Colombian Caribbean region has become an important exploratory target, and recent discoveries confirm its potential as a gas province to overcome the expected near-future gas deficit. A petrophysical and dynamic characterization workflow was implemented for this challenging deepwater play, where the depositional environment is the result of turbidity current processes. The reservoirs consist mostly of thin to very thin sand layers, corresponding mainly to the Ta, Tb, and Tc divisions of the Bouma sequence as observed in the cored intervals. Bouma divisions Td and Te are related with the lowest rock quality and represent the nonreservoir intervals. The greatest challenge in the characterization of this particular reservoir is the vertical resolution, given the very low thickness of the layers, which becomes very difficult to detect using standard resolution logs. Thus, tomography images, resultant CT-scan curves, and their integration with routine and special core analyses were used to reveal the true nature of this complex reservoir. The proposed methodology focuses on the integration of routine and special core analysis for the petrophysical and dynamic characterization of the reservoir, where the pore-throat-radius distribution from high-pressure mercury injection becomes the basis of the differentiation between what is considered reservoir and what is not. Pore-throat radius estimated from high-pressure mercury injection (R35) correlates extremely well with textural features and clay content in the rock; therefore, this parameter (R35) was used to define the different classes for rock typing. The approach taken was to develop a multilinear regression model of R35 as a function of very high-resolution tomography outputs in the cored zones and then see how it may be extrapolated to the uncored zones using available high-resolution logs. Special petrophysical analyses, such as NMR low field, porous-plate capillary pressure, electrical properties, and relative permeability curves (steady state), showed correlation with the defined rock types and, in turn, allowed for a determination of the gas accumulation potential of the area. Finally, rock and fluid (dry-gas) properties have been used to build a single-well radial model to design initial well tests (DST) and predict production performance from each interval (selective tests). The simulation model represents the lateral and vertical heterogeneity related to the geological environment (turbidites). The final results have defined the flow and shut-in times during tests to optimize the budget.


2021 ◽  
Vol 11 (4) ◽  
pp. 1609-1620
Author(s):  
Yong-li Gao ◽  
Pan Li ◽  
Teng Li

AbstractChang-10 reservoir in Wuqi–Ansai oilfield of Ordos Basin is restricted by its strong microscopic heterogeneity, complicated microscopic pore structure and unclear oil–water movement rules. The technology of nuclear magnetic resonance (NMR) is an excellent method to quantitatively evaluate the reservoir fluid of different pore structure types, and the microscopic experiments such as cast thin slices, scanning electron microscope (SEM) and high-pressure mercury injection were also used to analyze the differences in the occurrence features of fluid of different pore structure types and their influencing factors. The experimental results show that the sandstone types of Chang-10 reservoir in Wuqi–Ansai Oilfield are mainly medium-fine arkose and lithic arkose. The pore types are mainly intergranular pore, feldspar pore, turbiditic zeolite pore and cuttings pore. The combination type of pore-throat belongs to mesopore–micropore and microlarynx–microlarynx. By mercury injection experiment analyzed the characteristic of capillary pressure curve, Chang-10 reservoir in Wuqi–Ansai Oilfield pore structures is classified into Type I, Type II, Type III and Type IV due to the different movable fluid occurrence features. The occurrence features of movable fluid are obviously controlled by the pore-throat, and the orders of control effect from strong to weak are from Type I, Type II, Type III to IV The saturation of movable fluid gradually becomes low when the pore-throat radius decreases.


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