Optimum interval of artificial groundwater recharge wells, considering injection rate and economic feasibility

최명락,김규범 한국지질과학협의회 2023 Geosciences Journal Vol.27 No.1

Artificial recharge of groundwater increases the water level in an aquifer, which can be used for water security in a drought-prone region. This study was conducted to identify the interval of injection wells in a small basin upstream of a watershed. For the pilot test, 11 injection wells were installed, in which individual and simultaneous injections were performed. The rates of the individual and simultaneous injections ranged from 0.49–38.13 and 0.04–11.48 m³/d, respectively. Simultaneous injection resulted in a reduced injection rate of approximately 4.4–95.4% compared to that of individual injection owing to the interference effect of the injection wells. Moreover, the hydraulic conductivity of each well and the radius of influence were used to analyze the interference effect during injection using the Thiem-Dupuit equation. The interference effect between injection wells was evaluated by increasing the space from 2 to 15 m at four recharge lines (total length: 340 m) within the study area, and the expected injection rate was calculated as the rates of 220.85–58.95 m³/d. On the other hand, construction cost for installing injection wells became higher at 2 m interval than at 15 m. Therefore, there was no significant increase in construction cost per 1-m3 injection volume as well as decrease in total injection rate if the well interval was > 5 m and the optimum interval of injection well was suggested to be at least 5 m. Drought-prone areas are generally excluded from water-welfare benefits and are economically fragile; consequently, when developing an artificial recharge facility, injection wells should be designed considering the security of suitable amount of water with economic feasibility.

포항분지 해상 CO₂ 주입정 시추 완결 및 구축

원경식 ( Kyoung-sik Won ),이대성 ( Dae-sung Lee ),김상준 ( Sang-jun Kim ),최성도 ( Seong-do Choi ) 대한지질공학회 2018 지질공학 Vol.28 No.2

본 연구는 “포항분지 해상 소규모 CO₂ 주입실증 프로젝트”의 일환으로 경상북도 포항시 영일만에 설치된 해상 플랫폼에서 CO₂ 주입 실증을 위한 주입정 시추 및 완결(well drilling and completion)을 수행하였다. 주입정 시추(well drilling)는 포항분지 해상지역 퇴적지층에 설치한 해상플랫폼의 상부부터 해저면까지 케이싱 설치를 시작으로 단계별로 굴진 공경을 축소하면서 케이싱 설치 및 시멘트 그라우팅(cement grouting)을 시행하며 진행하였다. 최종심도 816.5m까지 공경 4 7/8 inch (Φ124 mm) 규격으로 굴진하여 심도 746.5∼816.5 m 구간에 유공 케이싱을 설치하여 주입구간을 형성하였다. CO₂ 주입을 위한 주입공 완결(well completion)을 위하여 주입관, 패커(packer), 주입탑(christmas tree)을 설치하였다. 주입공을 완결하고 주입 플랜트 설비를 설치하여 CO₂ 시험 주입을 성공적으로 수행하였다. 현재의 주입설비는 100톤 규모의 소규모 주입 실증을 위한 설비로서 향후 주입설비 격상을 통하여 총 1만톤의 중규모 실증 주입설비로 추가적인 연구개발을 진행하고 있다. In this study, as part of the “Small-scale CO₂ Injection-Demonstration Project in Offshore Pohang Basin”, we performed drilling and completion of a CO₂ injection well from the offshore platform installed in the Yeongil Bay, Pohang city, Gyeongsang buk-do. The drilling of injection well was carried out from an offshore platform installing on the sediment formations of the Pohang Basin. Drilling diameters were reduced by stages, depending on the formation pressure and groundwater pressure along a depth and the casing installation and cement grouting in drilled hole were performed at each stage. The injection well was drilled to a final depth of 816.5 m with a hole diameter of 4 7/8 inches (Φ124 mm) and the perforated casing for an injection section was installed in a depth of 746.5~816.5 m. Injection tubing, packer, and christmas tree were installed for the completion of an injection well for CO₂. The validation project of the CO₂ injection was accomplished successfully by drilling the injection well and installing the injection facilities, and through the suitable CO₂ injection process. The current injection facility is a facility for small-scale injection demonstration of 100 tons. In the case of large-scale demonstration facility test of a capacity of 10,000 tons, research is underway through the upgrading of the injection facilities.

Effects of pressure build-up and CO2 migration on brine production

한아름,김태희 한국지질과학협의회 2020 Geosciences Journal Vol.24 No.4

The need to reduce the maximum injection pressure has been considered an important subject for storage efficiency and safety. Brine extraction from the storage formation is one of the most reliable methods to manage formation pressure. When brine extraction is performed, it is very important to select the optimum location of the extraction well, where the storage efficiency can be maximized. In this study, the sensitivities of the distance between injection/extraction wells and the length or depth of extraction intervals was investigated with a 20,183 metric ton/year injection/extraction rate for 30 years. The injected CO2 moves upward by buoyancy and spreads horizontally along with the top of the storage formation. Therefore, CO2 was re-extracted through extraction wells in the case with fully perforated intervals. Even if the intervals were shorter than 20 m, CO2 was re-extracted with an extraction distance within 500 m from the injection well. Excluding scenarios with CO2 re-extraction, the injection pressures at injection wells were reduced by 71.7% and the volumes of CO2 plume increased by 18.8%, compared with the maximum pressure and the gaseous volume of CO2 in case 1. It was found that the shorter extraction interval of the well located in the bottom part of the reservoir can significantly improve the injection performance, thus reducing the chance of CO2 re-extraction. With the viewpoint of long-term injectivity, in general, it was confirmed that as the distance of brine extraction increases, the injectivity decreases. However, we could find a considerable exception in general trends. If the extraction well is located within the lateral extension range of the CO2 migration, brine extraction can limit the lateral migration of CO2 and consequently increase the overpressure induced by the injection. Therefore, when determining the optimal location of the extraction well, the expected migration range of CO2 as well as the distance to the injection well, the depth and length of the extraction interval should be considered.

지하수 모델링 기법을 이용한 인공함양정 최적 위치 평가

이현주,구민호,김용철,Lee, Hyeonju,Koo, Min-Ho,Kim, Yongcheol 한국지하수토양환경학회 2014 지하수토양환경 Vol.19 No.3

A Fortran program was developed to determine the optimal locations of an artificial recharge well. Three objective functions were considered: (1) maximizing the recovery rates, (2) maximizing the injection rates, and (3) minimizing the coefficient of variation of the increased pumping rates. We also suggested a new aggregate objective function which combined the first and the third objective functions. The model results showed that locating the injection well inside the cluster of pumping wells was desirable if either the recovery or the injection rate was taken into account. However, the injection well located outside the cluster evenly increased the pumping rates in existing pumping wells. Therefore, for clustered pumping wells, installing an injection well at the center or the upstream of the pumping wells seems beneficial. For linear arrangement of pumping wells parallel to the constant head boundary, locating the injection well in the upstream was recommended. On the contrary, in case of the linear arrangement perpendicular to the constant head boundary, the injection well installed on both sides of the central part of the pumping wells was preferable.

염수 대수층 내 담수 주입양 변화에 따른 주입정과 양수정 사이의 담수체 거동에 관한 수치적 연구

정우창 한국수자원학회 2015 한국수자원학회논문집 Vol.48 No.1

In this study, the behavior of fresh water body between the injection and production wells with the fresh water injection rate in a saline aquifer is numerically analyzed by using a three-dimensional numerical model. 8 injection wells are arranged at equidistant intervals on a concentric circle and one production well is located at the center of this circle. In the case that the fresh water injection rate is relatively small, the fresh water body around a injection well screen is not mixed with neighboring ones and is independently distributed. However, when the injection rate is increased, the size of the fresh water body is continuously increased, and the areas, where saline and fresh water among injection wells are mixed, are appeared. The mixed degree is increased as the injection rate is increased. This phenomenon is identically generated around the production well. Moreover, when the injection rate is increased, the ratio of saline water in and around the production well is decreased.

Effects of Horizontal and Vertical Well Patterns during Waterflood in Anisotropic Reservoirs

이근상 한국자원공학회 2010 Geosystem engineering Vol.13 No.1

Using horizontal wells in a waterflood process,higher sweep efficiency is expected compared with the use of conventional patterns by vertical wells. However, the use of horizontal wells is very sensitive to the well pattern designed to operate the process. This paper presents an analysis of how the overall performance of a waterflood process is influenced by the well pattern using horizontal injector and producer in different configurations. The potential for a horizontal well application was assessed by numerical modeling for different scenarios in combinations of injection and production wells and reservoir anisotropy. Results from the study have demonstrated that significant amount of additional oil can be recovered and injectivity was remarkably improved by utilizing a combination of horizontal wells. The improvement of injectivity through a horizontal injection well was higher when it was combined with horizontal producer parallel to the injector. The overall performances in anisotropic reservoirs strongly depend on the type of wells considered and the orientation of the horizontal wells with respect to the permeability directions. Combination of horizontal wells placed parallel to the low permeability direction yields the best performance.

Effects of Horizontal and Vertical Well Patterns during Waterflood in Anisotropic Reservoirs

Lee, Kun-Sang 한국암반공학회 2010 Geosystem engineering Vol.13 No.1

Using horizontal wells in a waterflood process, higher sweep efficiency is expected compared with the use of conventional patterns by vertical wells. However, the use of horizontal wells is very sensitive to the well pattern designed to operate the process. This paper presents an analysis of how the overall performance of a waterflood process is influenced by the well pattern using horizontal injector and producer in different configurations. The potential for a horizontal well application was assessed by numerical modeling for different scenarios in combinations of injection and production wells and reservoir anisotropy. Results from the study have demonstrated that significant amount of additional oil can be recovered and injectivity was remarkably improved by utilizing a combination of horizontal wells. The improvement of injectivity through a horizontal injection well was higher when it was combined with horizontal producer parallel to the injector. The overall performances in anisotropic reservoirs strongly depend on the type of wells considered and the orientation of the horizontal wells with respect to the permeability directions. Combination of horizontal wells placed parallel to the low permeability direction yields the best performance.

수치모델을 이용한 소분지에서의 지하수 인공함양 효과 예비 평가

최명락 ( Myoung-rak Choi ),차장환 ( Jang-hwan Cha ),김규범 ( Gyoo-bum Kim ) 대한지질공학회 2020 지질공학 Vol.30 No.3

본 연구에서는 현장 주입 시험 및 3차원 수치모델을 이용하여 상류 소분지에서의 수직정을 이용한 지하수 인공함양 효과를 예비 평가하였다. 현장 주입 시험의 주입량, 지하수위 및 입도 분석 자료에 의한 수리 전도도 등을 이용하여 모델의 공당 주입량을 20, 37.5, 60, 75 m³/day로 설정하였으며, 주입 간격에 따른 총 28개의 경우에 대하여 MODFLOW를 활용한 수치모델을 실시하여 지하수위 및 물수지 변화를 분석하였다. 주입 후 주변 관측정에서의 지하수위 상승이 공당 주입량과 비례적인 선형 관계를 보이진 않았으며, 주입 간격이 길어지면 누적 효과가 감소하여 최대 수위상승 시기가 짧아지는 것으로 나타났다. 또한 4가지 경우의 공당 주입량을 매일 연속으로 주입하여 총량 1,200 m³을 주입할 경우, 주입량 대비 36.5~65.3%의 함양 효과가 나타나는 것으로 분석되었다. 그러나 장기간의 가뭄에 대응하고 보다 지속적인 양수를 위해서는 차수벽 등 지하수 저류시설을 병행한다면 보다 효과적일 것으로 보이며, 추후 주입 시설의 최적화 및 함양-취수의 시나리오 확보를 통하여 안정적인 인공함양 시스템 구축이 가능할 것이다. In this study, the effects of groundwater artificial recharge through vertical wells in the upper small basin are preliminarily evaluated by using field injection test and a 3-D numerical model. The injection rate per well in a model is set to 20, 37.5, 60, and 75 m³/day based on the results of field injection test, groundwater levels, and hydraulic conductivities estimated from particle size analysis, and a numerical model using MODFLOW is conducted for 28 cases, which have diverse injection intervals, in order to estimated the changes of groundwater level and water balance after injection. Groundwater level after injection does not show a linear relationship with the injection rate per well, and the cumulative effect of artificial recharge decreases and the timing of maximum water level rise is shortened as the injection interval becomes longer. In four cases of continuous injection with total injection rate of 1,200 m³, it is revealed that the recharge effect is analyzed as 36.5~65.3% of the original injection rate. However, it will be more effective if the artificial recharge system combined with underground barrier is introduced for the longer pumping during a long and severe drought. Additionally, it will be possible to build a stable artificial recharge system by an establishment of efficient scenario from recharge to pumping as well as an optimization of recharge facilities.

폴리머 공법 프로세스에 대한 수평 주입정 및 생산정의 적용

이근상 한국자원공학회 2010 한국자원공학회지 Vol.47 No.3

This numerical study was undertaken to investigate and compare the performance of polymer flood processes through different combination of horizontal and vertical wells for injection and production. IMEX, the three-dimensional numerical reservoir model of Computer Modeling Group, is used to analyze the performance of the reservoir. The potential for a horizontal well application was assessed through different scenarios in combinations of injection and production wells and reservoir area and thickness. For different parameters of the reservoir system, performances were compared in terms of cumulative oil recovery and water-oil ratio at the production well and bottomhole pressure or injectivity at the injection well. Results from the study have demonstrated that additional oil can be recovered and injectivity was significantly improved by utilizing a combination of horizontal wells when the same multiple constraints are assigned for injection and production wells. The improvement of injectivity through then horizontal injection well was higher when it was combined with horizontal producer. Properties of polymer and reservoir rock such as reservoir thickness and well spacing are also shown to impact the predicted injectivity. 본 수치 연구는 수평정과 수직정을 주입 또는 생산에 이용한 폴리머 공법 프로세스의 수행을 비교하기위한 것이다. Computer Modeling Group의 3차원 저류층 시뮬레이터인 IMEX를 사용하여 저류층 수행을 분석하였다. 서로 다른 주입-생산정 조합과 저류층 면적 및 두께에 대한 시나리오를 통하여 수평정 적용의 가능성을평가하였다. 서로 다른 인자들을 적용한 저류층 시스템에 대하여 생산정에서의 누적 오일 회수량과 물-오일비, 주입정에서의 공저압력 또는 주입도를 비교하였다. 본 연구의 결과에 따르면 복수의 제한 조건이 주입 및생산정에 설정되었을 때 수평정을 이용하면 주입도가 현저하게 개선되었다. 수평 주입정을 수평 생산정과 함께사용하면 주입도는 더욱 개선되고 오일 회수량이 증가한다. 정 간격, 저류층 두께 등의 저류층 특성도 주입도예측치에 영향을 미친다.

Pump-Probe Study of Carrier-Spin Injection in a Diluted Magnetic Double Quantum Well of CdMnTe/CdTe

A. Murayama,K. Nishibayashi,N. Kono,K. Saito,I. Souma,Y. Oka 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1

We study the dynamics of carrier-spin injection in a diluted magnetic semiconductor double quantum well (DMS-DQW) of CdMnTe/CdTe by means of pump-probe absorption spectroscopy. The time dependences of the absorption saturation intensity show the injection dynamics of spinpolarized electrons and heavy holes (hhs) from the DMS-CdMnTe into the non-magnetic CdTe wells, where separate tunneling of the electron and the hh is directly elucidated with time constants of 150 ps and 1 ns, respectively. The degree of circular polarization P of the absorption saturation increases from 0 to 70 ps after pumping in the non-magnetic CdTe well, which is caused by the injection of polarized electron spins in the DMS well. We observe a systematic dependence of the rise time of P on the magnetic eld. The faster polarization of the electron spin in the DMS well results in a faster electron-spin injection. The electron's spin polarization is accelerated in the DMS well by LO-phonon scattering at 6 T, where the electron spin splitting is close to the one-LO-phonon energy, which enables us to demonstrate a fast electron-spin injection with a time constant of 10 ps. We study the dynamics of carrier-spin injection in a diluted magnetic semiconductor double quantum well (DMS-DQW) of CdMnTe/CdTe by means of pump-probe absorption spectroscopy. The time dependences of the absorption saturation intensity show the injection dynamics of spinpolarized electrons and heavy holes (hhs) from the DMS-CdMnTe into the non-magnetic CdTe wells, where separate tunneling of the electron and the hh is directly elucidated with time constants of 150 ps and 1 ns, respectively. The degree of circular polarization P of the absorption saturation increases from 0 to 70 ps after pumping in the non-magnetic CdTe well, which is caused by the injection of polarized electron spins in the DMS well. We observe a systematic dependence of the rise time of P on the magnetic eld. The faster polarization of the electron spin in the DMS well results in a faster electron-spin injection. The electron's spin polarization is accelerated in the DMS well by LO-phonon scattering at 6 T, where the electron spin splitting is close to the one-LO-phonon energy, which enables us to demonstrate a fast electron-spin injection with a time constant of 10 ps.