Evaluation Of Wettability Of Altered Volcanic Reservoir Based On Logging Data

Reservoir wettability is a comprehensive reflection of the interaction between pore fluid and rock matrix in the reservoir.It is a key factor affecting the dynamic characteristics of oil and gas reservoirs,and also affects the migration and accumulation of oil and gas.Because wettability affects the saturation index9)by controlling the distribution of fluids,wettability affects the calculation accuracy of saturation.At present,there are two main problems in the study of reservoir wettability.One is that the current research methods are mostly carried out in the laboratory,which is time consuming and labor consuming.Another problem is that the wettability of rock may be changed by external factors in core drilling and experimental transportation.Therefore,the above two problems can be avoided by directly judging the wettability through logging data.It is generally believed that nuclear magnetic resonance(NMR)is very sensitive to the strength of fluid-rock interaction.Therefore,NMR has been considered as one of the best methods for wettability measurement since the 1950s.Therefore,the main purpose of this paper is to realize the wettability evaluation based on logging data.The main research contents of this paper are divided into six parts.(1)The wettability of rock and its influencing factors are comprehensively studied,and the current methods for measuring wettability are compared and understood.The contact angle measurement method suitable for this study area is selected as the wettability judgment comparison experiment.(2)Wettability of altered volcanic reservoir of Huoshiling Formation in Longfengshan area was evaluated by wetting angle measurement method;(3)The influence of different clay mineral components on the wettability of volcanic reservoir was analyzed,and the wettability of single clay mineral was studied using artificial rock samples.The experiment shows that chlorite is positively correlated with wettability.With the increase of chlorite content,the rock is more inclined to oil wettability.Montmorillonite,illite will make the rock more inclined to moisture;By analyzing the relationship between wettability and saturation index9),it is obtained that wettability is proportional to the value of n.Based on the relationship between the two,the relationship between NMR T2 spectrum and logging data and9)is studied respectively,the aim of it is to achieve the purpose of judging reservoir wettability.(4)The influence of wettability on the NMR T2 spectrum of rock was studied,and the influence of chlorite content of rock samples on the migration of the main peak of NMR T2 at different frequencies was analyzed.It was found that under the condition that other parameters were consistent,with the increase of frequency,the higher the chlorite content was,the higher the migration degree of the main peak of NMR T2 spectrum of rock samples to the left was.At the same frequency in the laboratory,I studied the relationship between the change rate of NMR porosity component and saturation index9)when the transverse relaxation time is 0.1ms.(5)Using conventional logging data and nuclear magnetic logging data to calculate9)and cementation index8)respectively,and to achieve the purpose of directly using logging data to judge reservoir wettability.(6)Combined with the actual formation situation in the study area,the degree of alteration of volcanic reservoir is judged by defining a new alteration factor,and the influence of alteration on reservoir evaluation is analyzed.