Issue
Korean Chemical Engineering Research,
Vol.45, No.6, 638-647, 2007
생산유전의 CO2 공법 적용성 평가를 위한 평가차트 개발 및 응용
The Development of Evaluation Chart for the Applicability of CO2 Flooding in Oil Reservoirs and Its Applications
본 연구에서는 회수증진기법 중 하나인 CO2 공법을 생산유전에 적용할 경우, 적용성 여부를 간단하고 정량적으로 평가할 수 있도록 하기 위한 평가차트를 개발하였다. 이 평가차트는 소스의 이용성, CO2-오일의 혼합도, 저류층 및 오일 특성의 적정성, 주입기법의 평가항목으로 구성되어 있다. 저류층 및 오일의 특성에서 오일 비중, 오일 점성도, 오일 포화도, 저류층 온도 및 투과도의 기본평가항목에 대해서는 점수로 평가되며, CO2 순도, 저류층 두께 및 경사도 등의 추가평가항목에 대해서는 상 ·중 ·하로 구분하여 정량적으로 평가된다. 또한 미서블공법의 주입기법 평가에서는 지층경사, 수직투과성 및 저류층 두께 등에 따라 연속주입공법과 WAG(CO2) 공법의 여부가 정성적으로 평가된다. 이와 같이 구성된 평가차트에 대해 CO2 공법이 성공적으로 수행된 51개 유전의 적용사례를 분석하여 이를 토대로 CO2 공법이 가능한 추천점수를 설정하였다. 본 연구에서 개발한 평가차트를 국내 기업이 참여중인 스코틀랜드의 캡틴 생산유전과 베네수엘라의 오나도 생산유전에 적용하여 CO2 공법의 적용 가능성 여부를 평가하였다. 여기서 캡틴 유전은 저류층의 공극률과 투과도가 매우 양호하나, C21+ 이상의 무거운 탄화수소 함유량이 54%를 넘는 중질유이다. 따라서 이러한 중질오일은 CO2와 비미서블공법으로 진행되므로 비미서블공법 기준하의 기본평가항목에 대해서만 평가한 결과 비미서블 CO2 공법이 적정한 것으로 평가되었다. 한편, 베네수엘라의 오나도 유전에 대해서는 최소 미서블압력이 저류층 압력보다 낮게 산출되어 미서블 CO2 공법이 적용 가능할 것으로 평가되었다.
In this study, we present the evaluation chart for assessing the applicability of CO2 flooding method to oil reservoirs. The evaluation chart consists of four categories as source availability, miscibility, applicability and injecting method of miscible flooding. The applicability of reservoir and oil in the chart has basic items of the properties such as oil gravity, viscosity, oil saturation, reservoir temperature and permeability, and these are quantitatively graded. Meanwhile, for additional items of CO2 purity, reservoir thickness and formation dip, they are graded as “highmediumlow”. In the case of evaluating the injection method of either continuous injection or WAG (CO2), the qualitative decision will be made according to formation dip, vertical permeability, reservoir thickness, etc. The recommended score in the chart was assigned by utilizing 51 oil producing fields which CO2 flooding is successfully being applied. The evaluation chart developed in this work has been applied to the Captain oil producing field located in Scotland as well as to the Onado oil field of Venezuela, which Korean oil companies have participated in. For the Captain field, the reservoir quality in terms of permeability and porosity is considered to be very excellent to flow the oil. The oil in captain field contains heavier component of C21+ as 54%. Therefore, this heavy oil could be immiscibly displaced, hence the evaluating result with the basis of immiscible criteria shows that CO2 immiscible flooding in this field could be properly applied. In the case of Onado oil producing field, since the estimated minimum miscibility pressure is lower than the reservoir pressure, it was assessed that the Onado field would be efficiently conducted for CO2 miscible flooding.
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