A New Management Strategy for Dead Oil Reservoirs With a Strong Aquifer

Abstract

A reservoir management strategy is presented, based on a pressure-production behavior analysis, which was carried out using data from a Llanos Basin's field in Colombia, applying the concept of Darcy's Law and Babu-Odeh Equation for verticaldeviated and horizontal wells respectively. The analysis can be applied on dead oil reservoirs (P res > P b ) providing a surveillance tool for making right decisions regarding the drawdown application as the well is produced, and thus maximizing the recovery factor.The methodology allows the estimation of the dynamic evolution of skin factor, pressure drawdown and water saturation by well, which are related as well to variables such as water cut (W cut ) and P wf for an easy handling and understanding of the field for geoscientists, reservoir and production engineers.This methodology could be applied without the necessity to build a previous simulation model, but in this case a simulation model was carried out, in order to validate the input data, obtaining a good history match. As a result of this, the methodology and numerical simulation model are complementary themselves.For this case, it was possible to define the proper/wrong application of drawdown increments that improve/reduce (mainly because of sanding) the productivity of vertical, deviated and horizontal wells for specific ranges of water cut. 2 SPE 132698 Simulation Model The current simulaton model is based on the layer cake model because all the 16 drilled wells are currently along the fault only. The main characteristics are: Total cells: 52x318x15 = 248,040 Active cells: 46,514 Porosity range: From 13 to 30% Permeability range: From 100 to 4000 mD K y = K x K z = [1 to 15%] K x Initial Water Saturation: 22% Initial conditions for equilibrium Black oil (P b = 167 psi; R s = 20 scf/stb) 2 phases flow P i = 1640 psia @ Datum: -3418 ft TVDss WOC = -3452 ft TVDss P cow = 0 psia Aquifer Volume: Infinite Primary Control: Liquid rate Secondary Control: Historical values of Bottom hole flowing pressures (P wf )The history match was based on tuning of K z /K x ratio and the oil-water relative permeability curves (K ro, K rw ) implemented. The (K ro, K rw ) curves were taken from the simulation model of two analog fields located at the Llanos Basin too (where the company is partner). This set of curves was artificially created, but finally it works. We tried several sensitivity runs using Corey type curves without success, but it is pending to incorporate the curves from SCAL analysis. SPE 132698 Calculation of: φ, Ka, Sw and Vclay, per well Assumes Cutoff values of: φ, Ka, Sw and Vclay, per unit/sub-unit Perform Summation process using % φH and % KH and obtain: Average values per unit/sub-unit φ, Ka, Sw and Vclay. Calculation of the total average of absolute KH value per well. Conversion of the total average of absolute KH value per well to effective KH values per well using the Krow curve defined for your reservoir Effective KH from petrophysics = Efective KH from PBU ? No Yes Define Skin from Darcy's Law with initial ...