The Novel Flow Models And Applications Of Fractured Caved Carbonate Reservoirs

Fractured caved carbonate reservoirs are ubiquitous in the world and have great reserve,which is one of the main fields of increasing oil reserves and production in China.The reserve of fractured caved carbonate reservoirs can meet the future requirement of energy development.The research on fractured caved carbonate reservoirs is the basis of exploitation and development of this kind of reservoirs.Meanwhile,fractured caved carbonate reservoirs are characterized as complex pore structure,strong heterogeneity and anisotropy,large scale span of medium.Therefore,the researches on flow models of fractured caved carbonate reservoirs are significant.Based on the seismic data of exploited well,this paper establishes the flow models for different kinds of fractured caved carbonate reservoirs,and proposes the corresponding transient pressure and rate analysis methods.The software for dynamic data analysis and well deliverability evaluation of fractured caved carbonate reservoirs is developed.This software has been validated and improved by applying it on more than one hundred wells,which has been an important tool for the fractured caved carbonate reservoirs.The main contents of this paper are described as follows:(1)This paper establishes a flow model of fractured caved carbonate reservoirs which is applicable to the case when the wellbore is connected with the cave,and forms the corresponding pressure transient analysis method.Based on the seismic data of many field wells,this paper establishes the mathematical model and derives the semi-analytical semi-numerical solution of dimensionless bottom-hole pressure through the Laplace transform and numerical inversion algorithm.Meanwhile,the type curves of dimensionless bottom-hole pressure and derivative are plotted on the log-log plot.Moreover,the flow regimes are analyzed according to the asymptotic solution.Results show that the entire flow process can be divided into 5 regimes.The effects of each parameter on the type curves are investigated.Through an example field well,this paper presents the detailed process of pressure transient analysis and validates the accuracy of proposed model is validated.(2)This paper establishes a fl ow model of fractured caved carbonate reservoirs which is applicable to the case when the caves disperdly distribute in the formation,and forms the corresponding pressure transient analysis method.Based on the seismic data of many field wells,this paper establishes the corresponding mathematical model,and derived the solution of dimensionless bottom-hole pressure.Meanwhile,the type curves of dimensionless bottom-hole pressure and derivative are plotted on the log-log plot.The flow regimes of two-cave model are analyzed.Results show that the entire flow process can be divided into 8 regimes.Through comparing the type curves of single cave and multi caves models,the conclusion that the number of concaves in the type curves is equal to the number of caves in the formation can be drawn,The effect of controlling parameters on type curves are demonstrated.The application of proposed model on an example field well is presented to validate the accuracy.(3)Based on the previous two flow models,this paper forms the corresponding rate transient analysis method.According to the seismic data of many field wells,this paper establishes the corresponding mathematical model and derives the solution of dimensionless flow rate integral through the Duhamel theorem.Meanwhile,the type curves of dimensionless flow rate integral and integral derivative are plotted on the log-log plot.The flow regimes of two-cave model are analyzed,which show that the entire flow process can be divided into 5 regimes.By comparing the type curves of two-cave and three-cave models,it is easy to find that the conclusion that the number of concaves in the type curves is equal to the number of caves in the formation also stands for the rate transient analysis.The influences of each parameters on type curves are demonstrated.Through an example field well,this paper presents the detailed steps of rate transient analysis and verifies the accuracy of proposed model.(4)This paper proposes a new method for determining the deliverability equation of fractured caved carbonate reservoirs.Combining the solution of dimensionless bottom-hole pressure under the single flow rate and superposition principle,the expression of bottom-hole pressure difference under multi flow rates are constructed.Based on the above expressions,the computational method of deliverability equation is established,including the acquirement of dimensionless bottom-hole pressure and the calculation of deliverability equation two sections.Then,through applying the proposed method on two field wells,the detailed steps are presented and the accuracy is validated.Meanwhile,through the calculation of numerous field data,three constraints on the input parameters of proposed method are summarized and their necessities are proved,respectively.