Abstract
This paper describes a scale inhibitor (SI) screening study for
potential application offshore in high volume (30,000 STB per day) horizontal wells in a fractured chalk reservoir. In addition to scale inhibitor effectiveness, potential “pseudo scale” issues are highlighted by an examination of static scale inhibitor/rock interactions and surface analysis using SEM and EDAX techniques. This led to the selection of two generically different products for core flooding studies: a phosphonate based scale inhibitor (Phos) and a sulphonated – polyacrylate co-polymer (VS-Co). The first product (Phos), was a significantly more effective carbonate scale inhibitor; however static inhibitor/rock interaction studies indicated the potential for pseudo scale formation. Thus, in order to minimise the risk to production caused by the increased skin factor (associated with possible near wellbore plugging due to uncontrolled pseudo scale (Phos/Ca2+) precipitation), a less effective product (in terms of carbonate scale performance (VS-Co) was also selected for detailed evaluation in core flooding studies.
Results from the scale inhibitor core flooding studies and subsequent field application modeling using the Heriot-Watt University SQUEEZE V scale application software indicate, as expected, the potential for significantly longer field squeeze lifetimes when using the Phos based SI than would be expected
when examining the VS-Co species. However, significantly reduced permeabilities were recorded for the phosphonate based species as a result of Phos / Ca2+ in situ precipitation, which was clearly evident in post treatment SEM analysis.
In summary this paper describes a typical screening study for SI selection prior to field application. It demonstrates how appropriate chemical selection and field application modeling can highlight potential problems. This may then lead to the
selection of a poorer performing product (in terms of inhibition and potential squeeze lifetime) which may be the safest option due to potential formation damage arising from the application of an otherwise more effective product.
potential application offshore in high volume (30,000 STB per day) horizontal wells in a fractured chalk reservoir. In addition to scale inhibitor effectiveness, potential “pseudo scale” issues are highlighted by an examination of static scale inhibitor/rock interactions and surface analysis using SEM and EDAX techniques. This led to the selection of two generically different products for core flooding studies: a phosphonate based scale inhibitor (Phos) and a sulphonated – polyacrylate co-polymer (VS-Co). The first product (Phos), was a significantly more effective carbonate scale inhibitor; however static inhibitor/rock interaction studies indicated the potential for pseudo scale formation. Thus, in order to minimise the risk to production caused by the increased skin factor (associated with possible near wellbore plugging due to uncontrolled pseudo scale (Phos/Ca2+) precipitation), a less effective product (in terms of carbonate scale performance (VS-Co) was also selected for detailed evaluation in core flooding studies.
Results from the scale inhibitor core flooding studies and subsequent field application modeling using the Heriot-Watt University SQUEEZE V scale application software indicate, as expected, the potential for significantly longer field squeeze lifetimes when using the Phos based SI than would be expected
when examining the VS-Co species. However, significantly reduced permeabilities were recorded for the phosphonate based species as a result of Phos / Ca2+ in situ precipitation, which was clearly evident in post treatment SEM analysis.
In summary this paper describes a typical screening study for SI selection prior to field application. It demonstrates how appropriate chemical selection and field application modeling can highlight potential problems. This may then lead to the
selection of a poorer performing product (in terms of inhibition and potential squeeze lifetime) which may be the safest option due to potential formation damage arising from the application of an otherwise more effective product.
| Original language | English |
|---|---|
| Pages | 1-13 |
| Number of pages | 13 |
| Publication status | Published - Feb 2001 |
| Event | International Symposium on Oilfield Chemistry - Houston, United States Duration: 13 Feb 2001 → 16 Feb 2001 |
Conference
| Conference | International Symposium on Oilfield Chemistry |
|---|---|
| Country/Territory | United States |
| City | Houston |
| Period | 13/02/01 → 16/02/01 |