Abstract: Thin interbedded ultra-thick oil reservoirs are characterized by small net total thickness ratio, strong longitudinal inhomogeneity and severe steam overlap. In order to clarify the feasibility and influencing factors of steam flooding for enhanced oil recovery in such reservoirs, a study was made on the reservoir engineering optimization design by means of numerical simulation technology and dynamic analysis, taking Xinglongtai reservoir in Block Du 80 as the target, with reference to the successful experience of steam flooding in other types of ultra-heavy oil reservoirs. As found in the results, in Xinglongtai oil reservoir of Block Du 80, the mudstone interbed of about 5 m is stably developed, which can be subdivided into 2 development layers for independent development; the wells were arranged into inverted nine-spot pattern with well spacing of 70 m, the production and injection ratio was 1.1-1.2, the steam injection rate was 1.7-1.9 t/(d·m·hm²), the downhole steam dryness was greater than 50% as the best, and the time of flooding conversion is determined as the time when the reservoir temperature is greater than 80 ℃; the perforation density was determined as 4, 8, 12 and 16 holes/m respectively according to the thickness of the sub-layer and the range limit. The field pilot test of steam flooding has achieved good results in doubling the daily oil production and oil recovery rate of single well. The study results provide technical support for the conversion of development mode after steam stimulation in thin interbedded ultra-heavy oil reservoirs.

Key words: Thin interbed, ultra-heavy oil, steam flooding, pilot test, reservoir engineering