Comprehensive Performance Design Criteria for Hydraulic Fracturing

Abstract

Several works have tried to address hydraulic fracturing treatments using a unified theory approach based on the dimensionless productivity index concept. The observations and recommendations from these works are based on numerical simulation, resulting from single phase liquid and simplifications such as steady state or pseudo steady state conditions. However, the behavior in the reservoir is not a simplified one and the assumptions made previously by other authors limit the application of the technique. In this paper we present the correct and rigorous mathematical solution of the dimensionless productivity index. The application of a General Expression for Dimensionless Productivity in Bounded Reservoirs is presented and applied to multiwell systems Field examples and results are presented, where production analysis suggested changes and optimization of fracturing fluids, breakers, job sizes, designs, types and mass of proppant, etc. Guidelines for performance optimization and practical standards are obtained from field production results and are also presented. A General Expression for Dimensionless Productivity In this section we present the derivation of a general expression for the Dimensionless Productivity index. To do this, we need to understand the relation between steady state and pseudo steady state conditions in a bounded reservoir. As demonstrated by Poe[1], one of the fundamental inequalities that is applicable for the pressure and rate-transient behavior for all well types and flow regimes, including steady state and boundary-dominated flow in closed finite reservoirs, given by (1) It can be proved that for all flow regimes and well types, for a given tD (tDA, tDXf), the reciprocal of the wellbore rate-transient solution is greater than or equal to the corresponding pressure-transient solution. Equation 1 is the fundamental relationship between the reciprocal of the dimensionless wellbore rate-transient solution and the corresponding dimensionless wellbore pressure-transient solutions. In particular and only for steady state conditions, (constant pressure outer boundary conditions), the pressure and rate-transient behavior are given by

Design Criteria for Improved Performance of Fractured Wells

“…As demonstrated by Ramey and Cobb 6 , and later employed by other invetsigators [2][3][4][5] , the relationship between the classic wellbore pressure transient solution of a well (expressed in terms of a pressure drawdown applied to the system being the difference between the initial reservoir pressure and the sandface flowing pressure (P i -P wf )) and the dimensionless productivity index of a well during pseudosteady state flow (with a pressure drawdown referenced to the potential between the average reservoir pressure and the sandface flowing pressure ( r wf P P − )), is given by Eq. 2.…”

“…Since that time, a number of researchers [2][3][4][5] have developed interpretation models and analyses that employ the dimensionless productivity index as the basis for improved fracture stimulation design.…”

“…Direct field applications of this fracture stimulation design technique have been reported in the literature for moderate and high permeability reservoirs [2][3] . Extension of the single phase analyses that have been commonly employed in previous studies were later extended to consider multiphase flow, in an investigation that also involved the development of a dimensionless productivity index solution for vertically fractured wells in closed cylindrical and rectangularly bounded reservoirs 2 .…”

A Unique Methodology for Evaluation of Multi-Fractured Wells in Stacked-Pay Reservoirs Using Commingled Production and Rate Transient Analysis

“…With a focus on improving the production response and financial performance of the completions options. • The described methodology can be utilized to optimize the completion efficiency and productivity of wells completed in multilayer commingled reservoirs by; 1 Making use of information readily available for any well, production rates. No need to shut the wells for build-up testing, since the production data behaves as an extended drawdown (multirate) and by using superposition-in-time) 2 The Rate-transient diagnostics are effectively used to identify flow regimes and effective fracture properties, by identification of the fracture flow periods; bilinear, formation pseudo-linear or formation linear flow.…”

Production Performance Design Criteria for Hydraulic Fractures

“…One of the first investigations that specifically pertained to this subject was reported by Valko and Economides 1 . Subsequently, a number of other investigators [2][3][4][5] have developed interpretation models and analyses that employ the dimensionless productivity index as the basis for improved fracture stimulation design.…”