Application of conventional logging and gas logging data to fluid identification of carbonate reservoirs in K reservoir of H Oilfield

Abstract

K reservoir is an important oil and gas producing layer of H oilfield in the Middle East, Iraq. The reservoir space is mainly matrix pores and dissolved pores, with a wide range of permeability and poor correlation between porosity and permeability. The reservoir thickness is large, and the stratigraphic heterogeneity is very strong; therefore, it is poor quality to identify carbonate reservoir fluid properties only relying on conventional logging data and traditional logging evaluation methods. Aiming at this problem, the fluid identification work of K reservoirin H oilfield was carried out. By analyzing conventional logging data, it is found that the ratio of deep to shallow resistivity can better distinguish water from hydrocarbon. Based on analyzing morphological characteristics of the total hydrocarbon curve and corresponding reservoir fluid properties, it is found that the gas curve has obvious differences in the morphology of different fluid properties, so it is considered to further classify water and hydrocarbon by using gas curve. It is found that the ratio of heavy hydrocarbon tohydrocarbon gas density index can better classify oil-water layer and water layer. In order to quantitatively characterize the identification process, the identification method of water-oil-water layer gas measurement curve (ECR1) is established. ECR1 greater than 0 is oil-water layer, otherwise, it is water layer. Based on gas wet index, light hydrocarbon ratio and excavation effect, the identification method of gas-reservoir gas measurement curve (ECR2) is established. ECR2 higher than 0 isgas reservoir, and vice versa. The application of this model to 38 small layers in 13 wells of K reservoir in H oilfield shows that the recognition coincidence rate reaches 81.58%, and the recognition accuracy is high, meeting the actual needs of study area. The established ECR model has achieved good application effect in K reservoir of H oilfield, which can provide a certain reference for the subsequent exploration and development of this area, and also provide a reference for fluid identification of similar carbonate reservoirs worldwide.

Keywords

• k reservoir
• carbonate reservoir
• fluid identification
• gas logging
• excavation effect