Estimation of Formation Properties Using Multiprobe Formation Tester in Layered Reservoirs

Badaam, Hussein; Al-Matroushi, Salem; Young, N.B.; Ayan, Cansu; Mihcakan, M.; Kuchuk, Fikri J.

doi:10.2118/49141-ms

Cited by 13 publications

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“…Modular and multiprobe formation testers have proved advantageous in the determination of permeability at intermediate-scale lengths because of the increased distance between the observation and sink probes (Pop et al 1993;Badaam et al 1998;Proett et al 2000). Moreover, the use of dual-packer or "straddle-packer" modules over point-probe modules is known to improve the interpretation of pressure transient measurements when testing laminated, shaly, fractured, vuggy, unconsolidated, and low-permeability formations (Ayan et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Estimation of Permeability and Permeability Anisotropy From Straddle-Packer Formation-Tester Measurements Based on the Physics of Two-Phase Immiscible Flow and Invasion

et al. 2007

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We describe the successful application of a new method to estimate permeability and permeability anisotropy from transient measurements of pressure acquired with a wireline straddle-packer formation tester. Unlike standard algorithms used for the interpretation of formation-tester measurements, the method developed in this paper incorporates the physics of two-phase immiscible flow as well as the processes of mudcake buildup and invasion.An efficient 2D (cylindrical coordinates) implicit-pressure explicit-saturation finite-difference algorithm is used to simulate both the process of invasion and the pressure measurements acquired with the straddle-packer formation tester. Initial conditions for the simulation of formation-tester measurements are determined by the spatial distributions of pressure and fluid saturation resulting from mud-filtrate invasion. Inversion is performed with a Levenberg-Marquardt nonlinear minimization algorithm. Sensitivity analyses are conducted to assess nonuniqueness and the impact of explicit assumptions made about fluid viscosity, capillary pressure, relative permeability, mudcake growth, and time of invasion on the estimated values of permeability and permeability anisotropy.Applications of the inversion method to noisy synthetic measurements include homogeneous, anisotropic, single-and multilayer formations for cases of low-and high-permeability rocks. We also study the effect of unaccounted impermeable bed boundaries on inverted formation properties. For cases where a priori information can be sufficiently constrained, our inversion methodology provides reliable and accurate estimates of permeability and permeability anisotropy. In addition, we show that estimation errors of permeability inversion procedures that neglect the physics of two-phase immiscible fluid flow and mud-filtrate invasion can be as high as 100%. MethodThere are three main components in the workflow developed in this paper:1. Mud-filtrate invasion algorithm 2. Two-phase axisymmetric simulator 3. Nonlinear minimization algorithm Transient measurements of pressure and flow rate are compared to the outputs of a two-phase axisymmetric simulator to yield new model parameters through nonlinear minimization. The invasion algorithm makes use of these parameters (permeability and permeability anisotropy), in addition to pressure overbalance, invasion geometry, mudcake properties, and other rock-formation properties, to simulate the process of mud-filtrate invasion. Subsequently, the calculated spatial distributions of pressure and fluid saturation resulting from mud-filtrate invasion are used as initial conditions for pressure-transient tests. To reduce the time required by the inversion, this last step could be approximated with an invariant mud-filtrate invasion profile calculated only once during the minimization. However, such a strategy is not recommended for supercharged formations where updates of initial conditions during minimization can drastically impact inversion results. For the synthetic case examples cons...

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Section: Introductionmentioning

confidence: 99%

Estimation of Permeability and Permeability Anisotropy From Straddle-Packer Formation-Tester Measurements Based on the Physics of Two-Phase Immiscible Flow and Invasion

et al. 2007

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An Investigation of Near-Wellbore Flow Properties Using Sonic Scanner Measurements and Interval Pressure Transient Testing

Ayán

Petricola

Knight³

et al. 2007

SPE Annual Technical Conference and Exhibition

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Wireline Formation Tester (WFT) pretest success ratio (good versus tight pressure points) has been traditionally low in East Kalimantan-Indonesia over decades despite technological advances. One possible reason has been postulated as alteration of near-wellbore formation properties during drilling operations. The relatively tight gas sands are drilled with significant overbalance due to a mix of depleted and virgin zone layers using oil based mud systems. To further investigate possible near formation alteration, an extensive evaluation program was undertaken, using new generation sonic logs, WFT-multi-probe interval pressure transient testing (IPTT) and coring. A Sonic Scanner* survey was conducted in Tunu field to investigate possible nearby formation alteration, followed by MDT*-multi-probe IPTT. The Sonic Scanner dipole radial profiling showed some radial property change at several zones. The altered zone radial extent was quantified. The MDT-IPTT tests quantified the, virgin zone effective gas permeability and permeability anisotropy as well as gave a fair idea of the open hole skin factor. Combination of the results gave altered zone radius, altered zone permeability, virgin zone permeability and anisotropy on a comparative basis between different zones. Moreover, the results from both dipole radial profiling and MDT-IPTT indicated that formation alteration not necessarily increases with overbalance. The results quantified nearby formation alteration, showed this as a possibility and can further help in selecting the best perforation strategy. Introduction In the tight and laminated sands of East Kalimantan, Indonesia, obtaining pressures with Wireline Formation Testers has always been difficult. This naturally affects the success of sampling and downhole fluid analysis performed subsequently after the probe pressure measurements. Until recently, higher temperatures, six inch hole size and Oil Based Mud (OBM) limited the use of dual packer tools in this environment, which could be a better solution depending on the number of test points desired. Though the fine laminations of the tight gas sands is a major reason for observing low success statistics of communicating with the formation, other possibilities have been postulated. One of the possibilities is the alteration of near formation properties due to drilling fluid invasion. Some mechanisms that can cause damage due to OBM invasion are:Emulsion blocking - emulsions may form between the filtrate, formation fluids and connate water.Relative permeability effects - most pronounced in tight, water-wet gas sands where oil based mud filtrate is the third phase introduced into a two-phase system, thereby reducing the relative permeability to gas. This usually results in longer cleanup times, especially in tight formations.iii. Fines migration - another reason for near wellbore formation alteration could be wettability change due to OBM invasion. Such drilling fluids usually have surfactants as additives, and an excess amount may change the wettability of water wet particles in the formation to oil wet. These particles, which are originally immobile may then be mobilized and can cause near wellbore formation damage.iv. Plugging by particulates, particularly fluid loss control additives -certain additives may cause damage by plugging pore throats in an irreversible manner.

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A New Pressure/Rate Deconvolution Algorithm to Analyze Wireline Formation Tester and Well-Test Data

Pimonov

Ayán

Önür

et al. 2009

SPE Annual Technical Conference and Exhibition

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The deconvolved pressure change and its natural-logarithmic time (or Bourdet) derivative are very important for wellbore/reservoir system identification in pressure transient interpretation because they represent the constant-rate drawdown response of the system. In recent years, the use of pressure/rate deconvolution has increased considerably due to significant improvement of the mathematical algorithms. In this paper, we present a robust deconvolution algorithm based on a weighted Euclidean norm in the Tikhonov regularized objective function so that one can assign weights to individual pressure and rate measurement points, and thus define different error estimates for different sections of the data. Incorporating such features into the deconvolution algorithm is very useful to mitigate the effects of unreliable pressure and rate measurements and the sections of the data not obviously consistent with the wellbore/reservoir model. In the deconvolution algorithm, the Levenberg-Marquardt method with a restricted step procedure is used for the minimization of the objective function. We present several applications of the new algorithm using real field pressure/rate transient data sets. In addition to well test data, we apply the algorithm to wireline formation-tester pressure transients which are usually also referred to as Interval Pressure Transient Tests (IPTT). The examples include data with cleanup effects as well as an IPTT test, followed by a conventional Drill Stem Test (DST). To the best of our knowledge, applications of deconvolution to wireline formation-tester pressure transients have been limited to a single publication before. Hence, the deconvolution algorithm and the results in this paper will be useful in designing and interpreting wireline formation tester pressure transients in addition to pressure transient well tests.

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Estimation of Formation Properties Using Multiprobe Formation Tester in Layered Reservoirs

Cited by 13 publications

References 0 publications

Estimation of Permeability and Permeability Anisotropy From Straddle-Packer Formation-Tester Measurements Based on the Physics of Two-Phase Immiscible Flow and Invasion

Estimation of Permeability and Permeability Anisotropy From Straddle-Packer Formation-Tester Measurements Based on the Physics of Two-Phase Immiscible Flow and Invasion

An Investigation of Near-Wellbore Flow Properties Using Sonic Scanner Measurements and Interval Pressure Transient Testing

A New Pressure/Rate Deconvolution Algorithm to Analyze Wireline Formation Tester and Well-Test Data

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