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Method and Design to Characterize Stimulation Fluids at Conditions Similar to Field Conditions

IP.com Disclosure Number: IPCOM000238292D
Publication Date: 2014-Aug-14
Document File: 9 page(s) / 371K

Publishing Venue

The IP.com Prior Art Database

Abstract

Linear core flow wormholing tests are routinely used to characterize performance of matrix acidizing fluids. In this test, acid flows through a core sample at constant temperature, flow rate and back pressure and the acid volume required for breakthrough is estimated. Despite its popularity, upscaling of test results can pose some questions. The main drawback of the conventional linear core flow apparatus/core holder is that the interstitial velocity in the matrix is constant due to constant flow area. Further, there are questions regarding extrapolation of results from linear core flow tests to radial flow scenarios in real life situations. Additionally, it is difficult to capture the effect of completion type with the linear core flow test. Because of these issues it has become necessary to come up with an alternate experimental technique that will be quite close to realistic field scenario.

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Method and design to characterize stimulation fluids at conditions similar to field conditions

Abstract

Linear core flow wormholing tests are routinely used to characterize performance of matrix acidizing fluids. In this test, acid flows through a core sample at constant temperature, flow rate and back pressure and the acid volume required for breakthrough is estimated. Despite its popularity, upscaling of test results can pose some questions.

The main drawback of the conventional linear core flow apparatus/core holder is that the interstitial velocity in the matrix is constant due to constant flow area. Further, there are questions regarding extrapolation of results from linear core flow tests to radial flow scenarios in real life situations. Additionally, it is difficult to capture the effect of completion type with the linear core flow test. Because of these issues it has become necessary to come up with an alternate experimental technique that will be quite close to realistic field scenario.

In the present work, a new holder design and operational procedure is presented, described here as radial core flow, in which the fluid/acid flows in radial direction. Thus, the bottomhole flow regime is more closely replicated in accordance with the realistic bottomhole situation.

Introduction

A design and operational procedure for carrying of the acid wormholing tests much similar to downhole pumping technique is presented. Additionally, the method also allows for carrying out tests for diversion and for taking into consideration variations in minerology. Effect of different completion types (cased hole/open hole) can also be studied in the proposed design thus providing an experimental setup close to actual field scenarios.

Apart from just matrix acidizing, the technique can also be utilized for studying fracturing fluid

Evaluation, e.g., fluid loss, regain permeability, filter cake formation on inside core face similar to an actual wellbore. Furthermore, CT scans of these radial core samples provide means to visualize the wormhole branching in all directions. These results shed light upon the suitability of linear core flow tests in characterizing carbonate matrix acidizing and provided directions for improvement with regards to obtaining reliable numbers for scaled up field scenarios.

The apparatus design and experimental procedure are described below.

Core Holder Design

The radial core holder consists of a SS cylinder (e.g., 5-inch internal diameter and height of 8 inches) with a Teflon piston with O-ring placed in it. Simple criteria for selecting the core holder sizes are: diameter and height of core holder should be more than the diameter and height of cores sample under study. The thickness of a cylinder is selected as per the pressure rating required. A Teflon piston is placed inside the core holder. The Teflon piston has an O-ring placed in such way that it acts as perfect sealing for the zones above and below the piston. The core (e.g., 3...