Abstract:

Ordovician carbonate reservoirs in Qianmiqiao buried hill have experienced two periods of bare karst and post-Paleogene deep buried diagenesis. The bare karst during Indosinian-early Yanshan epoch, an important period for the formation of reservoir spaces, belongs to karst development mode of haystack hill-hollow type. Detailed study of 6 cementation events shows that deep-buried karst in Himalayan period, a critical period for the development of current reservoir pore system, is related to corrosive thermal fluids. The zones characterized by both local thermal fluid karst and surface karst under the outcropped anticlinal axes control the distribution of pores in Ordovician reservoirs in Qianmiqiao buried hill. Reservoirs are best developed in the anticlinal axes formed by compressional thrusting during the Indosinian epoch, especially in the areas where the shapes of anticlines within the buried hill harmonize with that of top of buried hill.

Key words: bare karst, burial period, diagenetic sequence, corrosive fluid, pore evolution