scholarly journals The efficiency of gas injection into low-permeability multilayer hydrocarbon reservoirs

2021 ◽  
Author(s):  
Sudad H Al-Obaidi ◽  
Hofmann M ◽  
Khalaf FH ◽  
Hiba H Alwan

The efficiency of gas injection for developing terrigenous deposits within a multilayer producing object is investigated in this article. According to the results of measurements of the 3D hydrodynamic compositional model, an assessment of the oil recovery factor was made. In the studied conditions, re-injection of the associated gas was found to be the most technologically efficient working agent. The factors contributing to the inefficacy of traditional methods of stimulating oil production such as multistage hydraulic fracturing when used to develop low-permeability reservoirs have been analysed. The factors contributing to the inefficiency of traditional oil-production stimulation methods, such as multistage hydraulic fracturing, have been analysed when they are applied to low-permeability reservoirs. The use of a gas of various compositions is found to be more effective as a working agent for reservoirs with permeability less than 0.005 μm2. Ultimately, the selection of an agent for injection into the reservoir should be driven by the criteria that allow assessing the applicability of the method under specific geological and physical conditions. In multilayer production objects, gas injection efficiency is influenced by a number of factors, in addition to displacement, including the ratio of gas volumes, the degree to which pressure is maintained in each reservoir, as well as how the well is operated. With the increase in production rate from 60 to 90 m3 / day during the re-injection of produced hydrocarbon gas, this study found that the oil recovery factor increased from 0.190 to 0.229. The further increase in flow rate to 150 m3 / day, however, led to a faster gas breakthrough, a decrease in the amount of oil produced, and a decrease in the oil recovery factor to 0.19. Based on the results of the research, methods for stimulating the formation of low-permeability reservoirs were ranked based on their efficacy.

Author(s):  
Sudad H AL-Obaidi ◽  
Miel Hofmann ◽  
Falah H. Khalaf ◽  
Hiba H. Alwan

The efficiency of gas injection for developing terrigenous deposits within a multilayer producing object is investigated in this article. According to the results of measurements of the 3D hydrodynamic compositional model, an assessment of the oil recovery factor was made. In the studied conditions, re-injection of the associated gas was found to be the most technologically efficient working agent. The factors contributing to the inefficacy of traditional methods of stimulating oil production such as multistage hydraulic fracturing when used to develop low-permeability reservoirs have been analyzed. The factors contributing to the inefficiency of traditional oil-production stimulation methods, such as multistage hydraulic fracturing, have been analysed when they are applied to low-permeability reservoirs. The use of a gas of various compositions is found to be more effective as a working agent for reservoirs with permeability less than 0.005 µm2. Ultimately, the selection of an agent for injection into the reservoir should be driven by the criteria that allow assessing the applicability of the method under specific geological and physical conditions. In multilayer production objects, gas injection efficiency is influenced by a number of factors, in addition to displacement, including the ratio of gas volumes, the degree to which pressure is maintained in each reservoir, as well as how the well is operated. With the increase in production rate from 60 to 90 m3 / day during the re-injection of produced hydrocarbon gas, this study found that the oil recovery factor increased from 0.190 to 0.229. The further increase in flow rate to 150 m3 / day, however, led to a faster gas breakthrough, a decrease in the amount of oil produced, and a decrease in the oil recovery factor to 0.19 Based on the results of the research, methods for stimulating the formation of low-permeability reservoirs were ranked based on their efficacy.


2021 ◽  
Author(s):  
Valentina Zharko ◽  
Dmitriy Burdakov

Abstract The paper presents the results of a pilot project implementing WAG injection at the oilfield with carbonate reservoir, characterized by low efficiency of traditional waterflooding. The objective of the pilot project was to evaluate the efficiency of this enhanced oil recovery method for conditions of the specific oil field. For the initial introduction of WAG, an area of the reservoir with minimal potential risks has been identified. During the test injections of water and gas, production parameters were monitored, including the oil production rates of the reacting wells and the water and gas injection rates of injection wells, the change in the density and composition of the produced fluids. With first positive results, the pilot area of the reservoir was expanded. In accordance with the responses of the producing wells to the injection of displacing agents, the injection rates were adjusted, and the production intensified, with the aim of maximizing the effect of WAG. The results obtained in practice were reproduced in the simulation model sector in order to obtain a project curve characterizing an increase in oil recovery due to water-alternating gas injection. Practical results obtained during pilot testing of the technology show that the injection of gas and water alternately can reduce the water cut of the reacting wells and increase overall oil production, providing more efficient displacement compared to traditional waterflooding. The use of WAG after the waterflooding provides an increase in oil recovery and a decrease in residual oil saturation. The water cut of the produced liquid decreased from 98% to 80%, an increase in oil production rate of 100 tons/day was obtained. The increase in the oil recovery factor is estimated at approximately 7.5% at gas injection of 1.5 hydrocarbon pore volumes. Based on the received results, the displacement characteristic was constructed. Methods for monitoring the effectiveness of WAG have been determined, and studies are planned to be carried out when designing a full-scale WAG project at the field. This project is the first pilot project in Russia implementing WAG injection in a field with a carbonate reservoir. During the pilot project, the technical feasibility of implementing this EOR method was confirmed, as well as its efficiency in terms of increasing the oil recovery factor for the conditions of the carbonate reservoir of Eastern Siberia, characterized by high water cut and low values of oil displacement coefficients during waterflooding.


Author(s):  
Mvomo Ndzinga Edouard ◽  
Pingchuan Dong ◽  
Chinedu J. Okere ◽  
Luc Y. Nkok ◽  
Abakar Y. Adoum ◽  
...  

AbstractAfter single-gas (SG) injection operations in tight oil reservoirs, a significant amount of oil is still unrecovered. To increase productivity, several sequencing gas injection techniques have been utilized. Given the scarcity of research on multiple-gas alternating injection schemes, this study propose an optimized triple-alternating-gas (TAG) injection for improved oil recovery. The performance of the TAG process was demonstrated through numerical simulations and comparative analysis. First, a reservoir compositional model is developed to establish the properties and composition of the tight oil reservoir; then, a suitable combination for the SG, double alternating gas (DAG), and TAG was selected via a comparative simulation process. Second, the TAG process was optimized and the best case parameters were derived. Finally, based on the oil recovery factors and sweep efficiencies, a comparative simulation for SG, DAG, and TAG was performed and the mechanisms explained. The following findings were made: (1) The DAG and TAG provided a higher recovery factor than the SG injection and based on recovery factor and economic advantages, CO2 + CH4 + H2S was the best choice for the TAG process. (2) The results of the sensitivity analysis showed that the critical optimization factors for a TAG injection scheme are the injection and the production pressures. (3) After optimization, the recovery factor and sweep efficiency of the TAG injection scheme were the best. This study promotes the understanding of multiple-gas injection enhanced oil recovery (EOR) and serves as a guide to field design of gas EOR techniques.


2021 ◽  
Author(s):  
Azat Albertovich Gimazov ◽  
Ildar Shamilevich Bazyrov

Abstract The article describes a method for developing low-permeability reservoirs using horizontal wells with multi-stage hydraulic fracturing. The effectiveness of the new method lies in protecting the horizontal part of the production well by drilling it through a non-reservoir plastic reservoir adjacent directly to the target reservoir. The paper considers various implementations of the technology and estimates the increase in oil recovery factor for each of them based on the results of hydrodynamic modeling. The risks associated with the implementation of the technology are considered. Methods for their reduction are proposed.


2021 ◽  
Author(s):  
Marut Wantawin ◽  
Thum Sirirattanachatchawan ◽  
Theerapat Suppachokinirun ◽  
Kittithuch Hnuruang ◽  
Sorawee Rongdechprateep ◽  
...  

Abstract Hydraulic fracturing activities implemented in Sirikit onshore oilfield of Thailand over a decade. Before 2018, the variation in post-fracturing production performance resulted in about 50% stimulation success rate. This outcome posted a big challenge to maintain project momentum. Hence, the candidate selection methodology was developed in-house which recommends "suitable" reservoirs. Using selection criteria, the multi-layered, low permeability reservoirs were selected for the 2018-19 Hydraulic Fracturing Campaign. Production analysis was conducted using the information gathered from past hydraulic fracturing campaigns. Reservoir Index (RI) was invented to distinguish the subsurface quality by formation permeability, thickness, pressure, and fluid properties. Together with the Fold of Increase (FOI) owing to hydraulic fracturing, a performance-based relationship was created which can categorize suitable reservoirs based on their RI ranges. This method has been applied to newly drilled wells during 2018. In the end, there were 13 wells selected to perform 28 hydraulic fracturing stages. The 2018-2019 Hydraulic Fracturing Campaign at Sirikit Oilfield was planned and executed. Post-fracturing production tests showing significant improvement. Some wells resulted in excellent oil production rate naturally, while some maintained high rate by artificial lift. According to post-campaign analysis, hydraulic fractures were proved to connect multiple layers of satisfactory flow capacity. In addition, well angle and stress direction accommodated the placement and orientation of multiple hydraulic fractures. As a result, the number of hydraulic fracturing stages that achieved economic production tests improved to 75% success rate. Hydraulic fracturing results from the past were fully utilized in order to achieve sustainable production improvement, thus driving continuous stimulation activities in the future. The candidate selection methodology has shaped up a candidate selection workflow that pointed out success criteria and avoided those that may lead to failure, which proved to be successful in one of the most complex fields in Thailand.


2021 ◽  
Author(s):  
Azat Albertovich Gimazov ◽  
Anzhelika Igorevna Balionis ◽  
Evgeniy Ivanovich Sergeev ◽  
Elmir Rovshanovich Khudiev ◽  
Ruslan Pavlovich Uchuev

Abstract To create a technology for selection the optimal RPM method the simulation on a sector hydrodynamic model of the field has performed. Different injection modes (continuous injection, alternating, cyclic), injection agents and completions of injection wells were tried during the modeling. The key factors, which influence the choice of the RPM method, were determined. Pilot industrial works include short-term nitrogen injection, long-term APG injection, and production from pilot wells in various modes. Well research include pressure testing, well testing after gas injection, recording of inflow profiles, laboratory studies of the Priobskoye field's own core. Evaluation of the potential of gas enhanced oil recovery methods shows their significantly higher efficiency compared to stationary waterflooding. The suggested approach can minimize the risks in the transition to previously untested development methods and methods of enhanced oil recovery in ultra-low-permeability reservoirs of the Achimov deposits. The analysis and the results of partially conducted pilot projects (at the moment) have showed a high potential for gas injection in certain areas of the field.


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