Theories of complicated identifications exchange

Abstract

The main objective of this study is to determine the pressure derivatives diagnoses for the infinite-conductivity horizontal well flow regimes identification which are not well studied so far in literature. The pressure derivatives diagnoses for the uniform-flux horizontal well flow regimes identification are fully studied in literature and presented here for comparison purposes only. The horizontal well flow regimes: early-radial, early-linear, late-radial, late-linear, and pseudo-steady state (PSS) are being identified. The identifications of flow regimes which have characteristic trends on log-log graph of pressure derivatives versus time represent unique technique in reservoir characterization. Five pressure derivatives are studied in detail: primary pressure derivative (PPD) (i.e., PPD=∂PD/∂tDA), Slope of PPD, PPD ×tDA, Bourdet derivative (i.e., tDA × PPD), and Slope of Bourdet derivative. For the first time, the pressure derivatives have been computed at high-resolution to diagnose the five infinite-conductivity horizontal well flow regimes identifications (i.e., the wellbore is discretized into twenty thousand of segments). In field application, synthetic pressure drawdown test data for infinite-conductivity horizontal well are analyzed by using type-curve matching technique.The novelties in this study are the following:1.The identifications of infinite-conductivity early-radial and early-linear flow regimes by Slope of Bourdet derivative are equal to −0.5 and 0 respectively which are different to their uniform-flux counterparts 0 and 0.5 respectively. Therefore, the pressure derivatives diagnoses are unique for a certain wellbore condition and there is a complicated identifications exchange between uniform-flux and infinite-conductivity flow regimes. The identification of infinite-conductivity early-radial flow regime is used for uniform-flux spherical flow regime and vice versa, and the identification of infinite-conductivity early-linear flow regime is used for uniform-flux early-radial and late-radial-flow regimes and vice versa.2.Theories of developing infinite-conductivity early-radial flow regime by multi aligned and merged uniform-flux spherical flow regimes and developing infinite-conductivity early-linear flow regime by multi aligned uniform-flux early-radial flow regimes are presented. The new theories prove the existence of the complex identifications exchange between uniform-flux and infinite-conductivity flow regimes.3.Without type-curve matching technique, downhole flow or pressure profile measurement, or presence of uniform-flux early-linear flow regime, or determination of mt at late-radial, late-linear, or PSS flow regime are crucial to distinguish if the wellbore is under uniform-flux or infinite-conductivity condition for correct horizontal well test analysis, mt = segments number of the half-length wellbore.4.At infinite-conductivity late-linear flow regime, qD distribution over the wellbore is uniform for any well and reservoir configuration as at infinite-conductivity PSS flow regime, qD = dimensionless inflow rate.