Abstract

Core flood tests are regarded as critical to qualification and optimization of scale inhibitors (SIs) deployed in "squeeze" mode, to assess both formation damage and chemical performance. However, the different test protocols commonly adopted can have significant impact on the outcome of both these aspects. Generally, SI core flood tests are designed to obtain both pieces of information from a single flood, often compromising the optimal testing of either or leading to chemical performance aspects being favoured over formation damage orvice versa.

Recent reports have illustrated how differences in test protocols can impact chemical performance results for clastic sandstones; the work presented in this current paper examines similar challenges in tight carbonate systems, such as those exhibiting both matrix and fracture flow. It demonstrates the importance of conducting core flood tests under representative conditions for these more reactive substrates in order to qualify chemicals appropriatelysuch that upscaling to the field case can be accurately achieved.

A suite of core flood tests were conducted on outcropcarbonate cores under matrix- and fracture-dominated flow conditions (simulating both macro and micro fractures), which allowed examination of chemical behaviour under different application conditions, thus highlighting differences in chemical-retention properties and associated treatment lifetimes as well as in formation damage assessment. This paper examines results from fractured carbonate core tests, which were designed to examine SI interaction and retention where chemical transport is dominated by diffusion, and compares these withsystems where transport is dominated by advective flow in the rock matrix. The overall aim was to examine the impact that core test design can have on the results observed and to discuss the consequences of different test approaches for chemical qualification. In summary, results show that different fracture apertures and flow conditions (matrix versus fracture flow) result in significant differences in formation damage and chemical retention, illustrating the importance of correctly replicating near wellbore conditions when designing such tests.

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