H. Cinco-Ley

Transient Pressure Analysis: Finite Conductivity Fracture Case Versus Damaged Fracture Case

This work presents the basic pressure behavior differences between a finite conduc tivity fracture and different types of damaged fractures. Two kinds of fracture damage conditions are studied: a) a damaged zone around the fracture, and b) a damaged zone within the fracture in the vicinity of the wellbore. The first case is caused by the fracturing fluid loss in the formation and the last case 1S originated by crushing, embedding or loss of propant within the fracture in the vicin ity of the wellbore. This paper emphasizes that although nite fracture conductivity and fracture damage condition are both flow restrictions, their effectson transient pressure behavior are quite different at early time. Type curves and both linear flow and bilinear flow graphs can be used to identify different cases when applied properly.

Application of the pressure derivative function in the pressure transient testing of fractured wells

A new technique is presented for the analysis of wells with finite conductivity fractures. The technique simultaneously uses the pressure and pressure derivative for the cases of no fracture face skin and no wellbore storage, and with fracture face skin and wellbore storage during bilinear flow. New type curves are presented and applied to three field cases. It concludes that using the pressure derivative with pressure behaviour type curves reduces the uniqueness problem in type curve matching and gives greater confidence in the results.

Pressure Transient Analysis for Naturally Fractured Reservoirs

New ideas are presented for the interpretation of pressure transient tests for wells in naturally fractured reservoirs. This work is based on the transient matrix flow model formulated by de Swaan. The differences between this model and the Warren and Root model occur during the transition flow period. It is demonstrated that the behavior of a naturally fractured reservoir can be correlated by using three dimensionless parameters. It is established that regardless of matrix geometry the transition period might exhibit a straight line whose slope is equal to half the slope of the classical parallel semilog straight lines, provided the transient matrix linear flow is present. In addition, information is provided on the estimation of fracture area per unit matrix volume or matrix parameters from the transition period semilog straight line. It is shown that matrix geometry might be identified when pressure data are smooth. Field examples are included to illustrate the application and the validity of the theoretical results of this study.

Application of the Pseudolinear-Flow Model to the Pressure-Transient Analysis of Fractured Wells

The theoretical basis for the pseudolinear-flow model is established. In this paper it is demonstrated by use of an analytical model that the linear-flow graph (rho vs. {Lambda}tau) can be extended to the analysis of pressure data of fractured wells intersected by an intermediate- or high-conductivity fracture (C/sub fD/ > 5{pi}). It appears that the fracture-conductivity effect during the pseudolinear-flow period can be handled as pseudoskin pressure drop that adds to the pressure drop caused by fluid-loss damage. The combination of the pseudolinear-flow analysis with other interpretation techniques is illustrated through examples of field cases.

Analysis of pressure tests through the use of instantaneous source response concepts

A general method of analysis for pressure transient tests is presented. This technique is based on the pressure response of an instantaneous source and it provides a mean to compute the first and second derivatives of the influence function (unit flow rate response) of the well-reservoir system. This information is basic in identifying the flow regimes occurring during the test. This method eliminates the effect of producing time on pressure buildup data. An explicit and stable procedure is discussed to compute both the derivatives of the influence function and the initial reservoir pressure. This technique is suitable for DST and Repeat Formation Tests as well as for pressure buildup and fall off tests with long shut in period; variable flow rate before shut in can be taken into account. Examples of application are presented.

The Influence of Vertical Fractures Intercepting Active and Observation Wells on Interference Tests

This paper reviews pressure behavior at an observation well intercepted by a vertical fracture. The active well was assumed either unfractured or intercepted by a fracture parallel to the fracture at the observation well. The authors show that a vertical fracture at the observation well has a significant influence on the pressure response at that well, and therefore wellbore conditions at the observation well must be considered. New type curves presented can be used to determine the compass orientation of the fracture plane at the observation well. Conditions are delineated under which the fracture at the observation well may influence an interference test. This information should be useful in designing and analyzing tests. The pressure response curve at the observation well has no characteristic features that will reveal the existence of a fracture. The existence of the fracture would have to be known a priori or from independent measurements such as single-well tests.

Detection of Linear Impermeable Barriers by Transient Pressure Analysis

This work presents a new simple method to detect a linear impermeable barrier by analysis of transient pressure data. This technique is based on the desuperposition method (negative superposition) discussed by some authors and considers the calculation the pressure change caused by the presence of the barrier. The pressure change is analyzed to estimate the distance between the well and the barrier by using the type curve matching technique. Type curves are provided for both drawdown and build tests. The advantage of the technique presented in this work is that pressure data can be analyzed even if the second semilog straight line, whose slope is twice the slope of the first semilog straight line, is not reached. Examples of application are discussed for illustration.

A strategic gas field development case in sandstones using seismic amplitudes and dynamic characterization

The objective of this paper is to present a process for improving the planning of gas field development. We discuss how static and dynamic characterization can be combined to help optimize gas field development. The main concepts, methodologies, and results are shown for an actual Mexican gas field. Static characterization centred on a series of seismic amplitude maps constructed from 3D seismic interpretation. Dynamic data included production data and initial pressure gradients which were useful in delineating individual reservoirs and establishing hydraulic communications between certain reservoirs. The seismic amplitude maps, modified by considering the dynamic data, improved the evaluation of reservoir quality, the estimation of drainage areas, original gas-in-place, and proved reserves. A strategy for the optimal field development was designed by using this combination of seismic amplitude maps modified with information from logs, cores, production, and pressure data.