By using core

thin section

SEM

porosity

permeability and geochemical data

this paper studied rock types

reservoir spaces and diagenesis of the Lower-Middle Carboniferous carbonate rocks in the coring interval of well A in Kenkyak area

Pre-Caspian Basin.The Lower-Middle Carboniferous carbonate reservoirs are grainstones and micrites of open platform facies with strong vertical heterogeneity and can be divided into two types

ClassⅠand ClassⅡ.The Class I is high quality reservoir with intergranular dissolved pores and intragranular dissolved pore as the main pore types.In contrast

the ClassⅡis moderate to poor reservoirs with pores dominated by intercrystalline pores and intercrystalline dissolved pores.Cementation and dissolution are the main diagenesis processes controlling the two types of reservoirs.The cementation mainly includes bladed-fibrous calcite cementation in normal seawater diagenetic environment and mosaic-granular-subhedral calcite cementation in burial diagenetic environment.The dissolution includes meteoric dissolution and burial dissolution

with the latter being critical for the formation of classⅠreservoir.The cementation is well developed in the classⅡ reservoir.