CCUS-EOR开发同步埋存阶段长度的确定方法

Method for determining time length of simultaneous sequestration phase of CCUS-EOR development

CCUS-EOR开发周期分为同步埋存和深度埋存两大阶段,确定同步埋存阶段长度是CCUS-EOR开发方案设计的一项重要内容。根据CO_(2)驱产油量变化情况,可将同步埋存阶段进一步划分为上产期、稳产期和递减期。上产期的时间长度由见气见效时的累积注入量与年注气速度计算,稳产期的时间长度即稳产年限借助气驱“油墙”集中采出时间测算,递减期内的阶段采出程度变化情况则利用典型产量递减规律研究,气驱产量递减率和稳产期采油速度需根据气驱增产倍数概念确定,从而建立了CO_(2)驱阶段采出程度评价数学模型,提出将阶段采出程度逼近最终采收率的时刻作为同步埋存阶段与深度埋存阶段的转换点并引入阶段转换判据;同步埋存阶段长度扣除上产期和稳产年限即为递减期的时间长度。

The life cycle of CCUS-EOR development can be divided into two parts.One is the simultaneous sequestration phase(SSP),and the other is the deep burial phase(DBP)of CCS.Determining the time length of SSP is an important part of CCUS-EOR development scheme design.According to the change trend of oil production under CO_(2) flooding,SSP can be further divided into an oil production rising period,a stable oil production period,and an oil production declining period.The time length of the oil production rising period is calculated from the annual gas injection rate and the cumulative injection amount at the gas emergence time.The time length of the stable oil production period under gas flooding is calculated by means of“centralized recovery time of oil bank”.The change of stage recovery during the oil production declining period is studied by using the representative decline curves.The oil recovery rate during the stable oil production period and oil production decline rate under gas flooding are measured based on the concept of“oil production multiplier due to gas flooding”.Thus,a mathematical model for evaluating stage recovery in the case of CO_(2) flooding is established.The moment when the stage recovery under CO_(2) flooding approaches the estimated ultimate recovery is proposed as the transition point between SSP and DBP.On this basis,a phase transition criterion is introduced.The time length of SSP minus those of the oil production rising period and the stable oil production period is the time length of the oil production declining period.