超稠油直井辅助双水平井SAGD井距界限研究

Study on Well Spacing Limit of SAGD in Dual Horizontal Wells Assisted by Vertical Well for Super Heavy Oil Reservoir

超稠油油藏SAGD开发受储层非均质性影响,出现水平段汽腔发育不均、横向扩展迟缓、开发效果不佳等问题,利用SAGD井组间原有直井上返补孔等措施对已投产的SAGD井组进行直井辅助,能够改善SAGD的开发效果。为了明确直井与SAGD井组间的井距界限,实现对辅助直井的科学选井,运用数值模拟方法,考虑非均质油层中水平段渗透率级差对沿程热损失以及传热效率的影响,解释了水平段沿程渗透率级差与汽腔发育程度之间的关系,并提出了以实现有效井间热连通为原则,依据SAGD井组水平段汽腔不同发育程度确定直井辅助SAGD井距界限的技术思路。数值模拟结果表明,不同类型汽腔的辅助半径存在不同的极限值,井距超出有效辅助半径时井间无法建立有效热连通,合理的井距能够显著提高油汽比及产油水平。

The development of SAGD in super heavy oil reservoir is affected by reservoir heterogeneity,which causes uneven development of horizontal steam chamber,slow lateral expansion and poor development effect.The development effect of SAGD can be improved by taking reperforating upwards and other measures for the original vertical wells among SAGD well groups.In order to define the well spacing limit between the vertical wells and SAGD well groups and to realize the scientific selection of vertical wells assisted,numerical simulation method is used.Considering the influence of horizontal permeability ratio on heat loss and heat transfer efficiency in heterogeneous reservoirs,the relationship between horizontal permeability ratio and development of steam chamber is explained.Based on the principle of effective inter-well thermal connection,the technical thought of determining the well spacing limit of SAGD in the vertical wells assisted is put forward according to the different development degrees of horizontal steam chamber in SAGD well groups.The numerical simulation results show that there are different limit values for the auxiliary radii of different types of steam chambers,and the effective heat connection between wells cannot be established when the well spacing exceeds the limit.Reasonable well spacing can significantly improve the oil-steam ratio and oil production level.