Journal of Petroleum & Environmental Biotechnology

Experimental study of characterization of aged fluid in casing annulus

6^th International Conference on Petroleum Engineering

June 29-30, 2017|Madrid, Spain

Efecan Demirci and Andrew K Wojtanowicz

Turkish Petroleum Corporation, Turkey
Louisiana State University, USA

Posters & Accepted Abstracts: J Pet Environ Biotechnol

Abstract:

In many cementing operations, the cement top does not reach to the surface. When this is the case, a cement-free casing annulus is formed between two casings, casing-head and cement-top. The fluid inside this confined space (annular fluid, AF) remains in place and ages. During a wellâ??s productive or abandoned life time, various operations concerning casing annulus may be required. If the condition of AF is unknown, applications may lead to ineffective results. Since the only access to any casing annulus is the top valve at the well-head, taking samples of the fluids from inside has not been practical. This paper aims to describe the final state of water-based AFs. Various AFs with different compositions were generated in the lab by changing the amounts of drilling mud, spacer and preflush; and a general formula of AF was determined. Then, long-term settling experiments were carried out by using a ten-foot PVC pipe. AFs were weighted up to 12.5 to 14.5 ppg and placed in the pipe; kept undisturbed for 3 to 11 weeks and densities of different levels were measured by taking samples. Lastly, mud column density distribution vs. time experiment was conducted in a twenty-foot physical model by recording pressure changes over time. As a result, the long-term settling experiments showed that the AF separates into three main zones: Compaction zone at the bottom, water zone at the top and a column of un-weighted mud in between. In majority of the experiments, compaction zone density varied between 19-20 ppg and was still able to transmit hydrostatic pressure. Based on the results, a mathematical barite bed height prediction model was derived. This study shows that the final condition of an AF column consists of three sections with different densities and any annular intervention attempt should be designed accordingly.

Biography :

Email: efecandemirci@gmail.com