| Carbonate karstic reservoir was distributed very widely and was becoming the main exploration target for increasing products in our nation. But the reservoir had the features of high heterogeneity in longitudinal and lateral, multiple reservoir controlling factors and hard geological model to build, so the reservoir prediction was the difficulty problem in worldwide. The research showed that the Ordovician carbonate prolific zone of the western LunGu area had relation to the weathered crust on the top of carbonate and dissolution cave inside carbonate. The geological model building of Ordovician carbonate karstic reservoir, reservoir identification from seismic and prediction, and the prediction of tectonic fracture controlling reservoir, were the key problems of efficient exploration and development of carbonate oil pool.In the paper, by the geological characteristics description of Ordovician karstic reservoir in the western LunGu area, the storage spaces of karstic reservoir were considered as solution pore, dissolution enlarged fracture, large solution cave and structural fracture. The karstic reservoir mainly contains four types, which were fracture, fracture-pore, pore, and cave. By the analysis of karstic reservoir development, the extent of karstification, palaeogeomorphology, the developing extent of faults and tectonic fracture, lithology, sedimentary and diagenesis, and packing action were considered as the main controlling factors of the reservoir. The karstification and regmagenesis due to tectonic movements were the main controlling factors to improve the storage space. The cementation, packing action and compaction were the main factors to increase the reservoir tightness and decrease the porosity. The palaeogeomorphology mainly had influence on the reservoir development scale and quality. The geological model was build for the first time by the analysis of these factors, and the rules of karstic reservoir development were summarized according to the study on other areas. The results showed that the reservoir can be divided into superficial karst zone, vadose karst zone, and underflow karst zone in longitudinal, and these three zones showed para-laminar distribution. The superficial karst zone was on the top of buried hill, with the thickness less than 50m. The main storage spaces were fracture and dissolution cave, and had good connectedness in lateral and storage capability. The vadose karst zone had the thickness about 30-120m. The main storage spaces were dissolution fracture, dissolution cave and hole. The sedimentary packing action was weak, and the effective storage spaces developed. The faults and fractures were the main controlling factors of reservoir in the zone. Below the vadose karst zone was the underflow karst zone, with the thickness about 50-80m. The dissolution fracture, dissolution cave and large hole were the main storage spaces. But the spaces were filled with arenaceous-pelitic matter frequently, which decreased the effective storage spaces. The main controlling factors of reservoir were dissolution and packing action. The development of karstic reservoir was mainly controlled by palaeogeomorphology, which can be divided into karstic highland, slope and depression. The karstic highland were suffered from atmospheric water, weathering and denudation, and lack of karstic reservoir. The karstic slope was the most developing unit of karstic reservoir, which suffered from the erosion and dissolution of atmospheric water, weathering and denudation, and surface runoff, and was easy to form storage spaces of dissolution fracture, cave and large holes. The karstic depression was on the gentle slope or depression of palaeogeomorphology, and was the location of current converging. The karstic reservoir were lack and also easy to be filled with arenaceous-pelitic matter.The different kinds of karstic reservoir were analyzed by forward method according to controlling factors and features. The reservoir was demarcated in seismic by well data, which proved the reservoir predictability by seismic data. The sensitive seismic attributes were filtered and analyzed, which showed that seismic amplitude, energy and frequency attributes were the sensitive to karstic reservoir.The reservoir of superficial karstic zone showed weak amplitude, high coherency (low correlation), low impedance and low frequency. The insider karstic reservoir showed strong amplitude, high energy, low frequency, and low impedance. The development of insider karstic reservoir caused amplitude change of seismic diffraction wave. The karstic cave reservoir had the characteristics of high amplitude, low tune and low velocity. The cave width mainly affected the seismic amplitude, and its height mainly affected the tune. The appearance of string beads depended on two factors: one was the scattered wave of cave had certain energy, and the other was the condition to form intense multiple. On general condition, multiple caves with certain width and distribution upper and lower were easy to form string beads, but the single large cave was hard.According to the study on the karstic reservoir of the western LunGu area, a set of reservoir comprehensive prediction and assessment techniques was summarized, which contained seismic attributes analysis (amplitude, energy, frequency and coherence), impedance inversion, palaeogeomorphology and tectonic fractures prediction, and multiple data combination. The relative merits and applicability of each single technique was summarized and evaluated, which showed using the single technique was hard to predict the reservoir precisely. So the combination of multiple techniques should be used to predict the reservoir more accurately and evaluate it more reasonably.Applying the geological model and the comprehensive prediction techniques for karstic reservoir summarized by the western LunGu area to the block of Weixinan in Zhanjiang and Saihantala depression in Erlian showed good application effect, which proved its good applicability, feasibility and validity, and can be spread and applied in other area.
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