Appropriate Simulation of Field Treatments Using Core Flood Data

Abstract

Core flood experiments are an integral part of the methodology for chemical selection and the optimisation of scale inhibitor treatments, providing information on formation damage, inhibitor return profile and the dynamic retention isotherm under post flush conditions (as a function of SI, brine, pH, rock matrix, T etc.). In the absence of formation damage, the comparative inhibitor returns are often used to select the chemical prior to field treatment. However, it is recognised that there can be significant discrepancies between the core data and field data, depending on how the tests are conducted and how the data are interpreted. In this paper, we describe the factors causing differences between the field and the core flood return. This includes inherent petrophysical differences between the small core plug and the larger near wellbore formation and differences in the saturation levels (e.g. core flood return typically at Sor) etc.. The paper also demonstrates that when considered appropriately, these differences should not impact the relative return profiles for different products. Other, more significant aspects however, often relate to artifacts of the core test design, e.g. oversaturation with pre-flush and main treatment solutions of which multiple pore volumes are commonly applied in core tests. This work will demonstrate that such aspects can have significant consequences for the comparative inhibitor returns and moreso that these can have considerably different impacts (order of magnitude) for different chemical treatments, especially when highly retentive products are being assessed. The result being that for ill suited test protocols, selection of less effective chemicals and poor initial treatment design can result. This paper presents examples of a series of core flood data in which the return profiles and derived isotherms show excellent agreement with field returns together with other examples were this is far from the case. We identify certain artifacts in commonly conducted core flood designs that should be avoided and recommend approaches and test protocols which allow more appropriate product ranking as well as modified modelling approaches which allow improved simulation from core to field..

Evaluation of Barium Sulfate Scale Inhibition Using Relative Permeability Modifier Polymers as Adsorption Enhancer for Mature Offshore Well Treatments in Campos Basin, Brazil

“…Test 1 inhibitor release curve presented the expected inhibitor release trend reported in literature. − Test 2, however, presented an atypical curve. Lithology of core sample for test 2 comprises less mineral variety than that of samples from test 1: In particular, no clay mineral was detected in core samples for test 2.…”

Effective Laboratory Simulation of Scale Inhibitor Squeeze Treatments -Core to Field II

“…During injection ( Figure 5) significantly higher retention of "apparent" inhibitor is recorded for assay by ICP (total P) with much lower retention when analysed by Hyamine (for polymer). Similarly in the PF stage, considerably higher apparent inhibitor concentrations are recorded based on ICP for total P. As described in previous works 22 the active inhibitor components are better determined the polymer assay content and such significant differences are not uncommon both in core studies and field returns. The differences relate to the presence of residual (non polymeric) reactive "P" containing components preferentially retaining onto the rock substrate.…”

“…In SPE 131131 22 it was shown that oversaturation has a significant impact on the behaviour of core-flood derived isotherms, due to the highly reactive nature of the acid phosphonate used in this test. Injection of multiple pore volumes of main treatment resulted in considerable oversaturation or overloading of the core with chemical.…”

“…Previous publications (SPE 131131 22 and cited work) discussed many such examples from various fields where well designed core flood treatments resulted in extremely good simulation of initial field tests. 4,13,21,22 (and many others within those refs).…”