Abstract:

The chlorite rims are frequently observed in clastic successions. Their content and

occurrence may heavily influence the reservoir properties. By using thin section determination and

SEM, BSE, EDX analyses, we studied occurrence, timing, mechanism of generation and contribution to

porosity preservation for the samples from Yanchang Formation, South Ordos basin. The results show:

(1) There exists a spatial coupling of chlorite development with the brackish water delta front

facies depositional environment and the biotite-rich arkosic sandstone; (2) The formation timing of

chlorite is not earlier than the initial compaction stage, but not later than the appearance of

authigenic quartz; (3) Formation of chlorite rims could change the porosity micro-environment and

prevent growth of authigenic quartz on the detrital quartz surface; (4) The intercrystalline pores

in chlorite rims are of limited value for petroleum storage, but can somehow contribute to the

reservoirs as pathways for acidic fluids circulation;
(5) The constructive diagenetic role of chlorite rims is their weakening effect for the overburden

stress and restricting effect for the autigenic quartz growth in certain degree.

Key words: chlorite rims, diagenesis, Ordos basin, authigenic quartz, reservoir