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This paper presents the results of an investigation concerning the development of a reliable and accurate technique for establishing the stabilized deliverability performance of multi-layer commingled systems using multi-rate production log measurements. Both linear and non-linear systems are addressed in this paper, providing a basis for the analysis of reservoirs exhibiting Darcy and non-Darcy flow, respectively. Extension of the conventional Selective Inflow Performance analysis is also presented in this paper to obtain estimates of the formation and well completion properties such as effective permeability, radial flow steady state damage /stimulation skin effect, and non-Darcy flow coefficient. In the specific case where the deliverability performance of a vertically fractured well is considered, estimates of the effective fracture half-length and average fracture conductivity may be derived from the analysis. In cases where the multi-rate deliverability tests are performed under boundary dominated flow conditions, conventional deliverability analysis techniques may also be employed to derive estimates of the reservoir drainage area in addition to the well and reservoir parameters that can be obtained in a transient flow analysis. Applications of the analyses reported in this paper demonstrate the use of the analyses to evaluate the inflow performance measurements of commingled multi-layer reservoirs obtained using multi-rate production logs. Introduction The analysis of the effect of a variable flow rate production history on the pressure transient performance of a well under Darcy flow conditions has conventionally been accomplished using the convolution of the varying flow rate and pressure history of the well to evaluate the transient performance. This relationship is presented in integral form in Eq. 1 and has been utilized for quite a long time1 in the analysis of the transient pressure behavior of oil and gas wells. (1) The dimensionless wellbore pressure at any point in time (tD) is shown to be a direct function of the varying flow rate and pressure history of the well prior to that point in time. The integral relationship given in Eq. 1 can be readily evaluated as a summation of discrete intervals of time for which the flow rate history is assumed to be piece-wise continuous, as a series of constant flow rate steps. This concept is expressed mathematically with Eq. 2 and has commonly been used as the basis for correlating the effects of a variable flow rate history on the pressure transient behavior of a well with the solution for a constant flow rate inner boundary condition. (2) The definitions of the dimensionless variables used in this superposition relationship are given in terms of consistent units for slightly-compressible liquid flow analyses with Eqs. 3 through 5 for time, flow rate, and wellbore pressure, respectively. In the case of an unfractured vertical well, the system characteristic length (Lc) is equal to the wellbore radius (rw).

This paper presents the results of an investigation involving the development of a reliable and accurate methodology for establishing the stabilized deliverability performance of multi-layer commingled reservoir systems using multi-rate production log measurements. Both linear and non-linear systems are considered in this work, providing a basis for the analysis of reservoirs that exhibit Darcy and non-Darcy flow, respectively. An extension of the conventional Selective Inflow Performance analysis is presented in this paper to obtain estimates of the formation and well completion properties such as effective permeability, radial flow steady state damage /stimulation skin effect, and non-Darcy flow coefficient. In the specific case where the deliverability performance of a vertically fractured well is considered, estimates of the effective fracture half-length and average fracture conductivity may be derived from the analysis. In cases where the multi-rate deliverability measurements are obtained under boundary dominated flow conditions, conventional deliverability analysis techniques may also be employed to derive estimates of the reservoir drainage area in addition to the well and reservoir parameters that can be obtained in a transient flow analysis. Applications of the analyses reported in this paper demonstrate the use of the analyses for evaluation of the inflow performance of commingled multi-layer reservoirs using multi-rate production log measurements. Introduction The analysis of the effect of a variable flow rate production history on the pressure transient performance of a well under Darcy flow conditions has conventionally been accomplished using the convolution of the varying flow rate and pressure history of the well to evaluate the transient performance. This relationship is presented in integral form in Eq. 1 and has been utilized for quite a long time1 in the analysis of the transient pressure behavior of oil and gas wells. Equation (1) The dimensionless wellbore pressure at any point in time (tD) is shown to be a direct function of the varying flow rate and pressure history of the well prior to that point in time. The integral relationship given in Eq. 1 can be readily evaluated as a summation of discrete intervals of time for which the flow rate history is assumed to be piece-wise continuous, as a series of constant flow rate steps. This concept is expressed mathematically with Eq. 2 and has commonly been used as the basis for correlating the effects of a variable flow rate history on the pressure transient behavior of a well with the solution for a constant flow rate inner boundary condition. Equation (2) The definitions of the dimensionless variables used in this superposition relationship are given in terms of consistent units for slightly-compressible liquid flow analyses with Eqs. 3 through 5 for time, flow rate, and wellbore pressure, respectively. In the case of an unfractured vertical well, the system characteristic length (Lc) is equal to the wellbore radius (rw).

TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractThis paper presents the results of an investigation concerning the development of a reliable and accurate technique for establishing the stabilized deliverability performance of multi-layer commingled systems using multirate production log measurements. Both linear and non-linear systems are addressed in this paper, providing a basis for the analysis of reservoirs exhibiting Darcy and non-Darcy flow, respectively.Extension of the conventional Selective Inflow Performance analysis is also presented in this paper to obtain estimates of the formation and well completion properties such as effective permeability, radial flow steady state damage /stimulation skin effect, and non-Darcy flow coefficient. In the specific case where the deliverability performance of a vertically fractured well is considered, estimates of the effective fracture half-length and average fracture conductivity may be derived from the analysis. In cases where the multirate deliverability tests are performed under boundary dominated flow conditions, conventional deliverability analysis techniques may also be employed to derive estimates of the reservoir drainage area in addition to the well and reservoir parameters that can be obtained in a transient flow analysis. Applications of the analyses reported in this paper demonstrate the use of the analyses to evaluate the inflow performance measurements of commingled multi-layer reservoirs obtained using multi-rate production logs.

This paper will evaluate the efficiencies of completion methods in a South Texas field utilizing the latest techniques in post fracture production analysis.Stimulation effectiveness for each frac stage in ten multi-zone wells is evaluated. Effective values for reservoir and fracture parameters including porosity, permeability, propped fracture half-length, fracture conductivity and fracture face skin will be derived using production analysis techniques and will be compared for the different completion methods employed.The holistic model will incorporate the geological, petro-physical properties of the formation and production logging data. Actual stimulation and production data from ten wells in the same area are used in this analysis. Five of the wells were completed in single-stage fracture stimulation across multiple perforated intervals.Five wells were completed with two-stage fracture stimulations across multiple perforated intervals.The multiple layer fracturing technique was utilized in all wells. The study will derive the effective reservoir and fracture parameters using production allocation for each interval in the multiple interval wells. This paper will compare the different completion techniques using this methodology and will discuss a predictive model for future stimulation work in this area.This methodology will also help in identifying under-stimulated zones in existing wells that may be candidates for re-fracturing. Introduction The wells included in the study are part of the Wilcox Lobo Trend located in Zapata County in South Texas.The Wilcox (Lobo) trend in Webb and Zapata counties is a series of geopressured, low permeability sands with an average depth from 5,000 to 12,000 ft (1,525 to 3,660 m).The Lobo section consists of a sequence of stacked Paleocene age sands and shales overlain by the Lower Wilcox shale of Eocene Age.Extensive faulting, present in the Lobo section, has resulted in a slump complex of rotated fault blocks.The Lobo trend extends from Webb and Zapata counties to the south and west into Mexico (Figure 1).Effective permeabilities are less than 0.1 md.Implementing an effective hydraulic fracture treatment and an evaluation process for stimulation effectiveness are requirements to economically produce the low permeability sands in the Lobo trend. The wells presented here are nearby offset wells in the Lobo field (Figure 2). These wells were completed in 2003.The target intervals in these wells are primarily three zones.All the wells were fractured with similar fracturing fluids, intermediate strength proppants and aggressive breaker schedules utilizing multiple layer fracturing techniques. Background Extensive work has been conducted around fracture treatment design and evaluation of wells with multiple zones with most of the work focused on the use of limited entry techniques to effectively place proppant across multiple zones [1,2,3,4].The limited entry technique utilizes perforation friction to divert designed fluid and proppant volumes into multiple zones.This method is utilized when the economics do not justify multiple stages or when multiple stages cannot be placed effectively[5].This technique has been successfully implemented in the Lobo field in numerous wells.The success comes from applying the formation evaluation and log analysis into a fracture modeling process, and from the use of limited entry design guidelines [6,7].Tracer surveys and production logs were obtained after numerous stimulation treatments to develop these guidelines.However, tracer surveys provide an estimate of the fracture height and production logs provide contributions from each zone in a snapshot of time.