An Integrated Experimental Workflow to Identify the Source of Formation Damage: A Well Case Study from an Offshore Oilfield, Malaysia
Authors: Hendraningrat Luky , Bin Che Mamat Che A Nasser , Binti Ramli Nora Aida , Bin Johar Razman Marsoff , Bin M Ibrahim Jamal Mohamad , Bin Mat Ismail M Shah , Riyanto Latief , Kin Chun Kok 
Published: February 2022

A naturally flowing well "C" was experiencing a sharp oil productivity decline (13%/month) and skin build-up was observed from well testing to ascertain quantitatively whether damage occurs. Meanwhile, asphaltenes and paraffins are well-known as the primary sources of organic deposition that can compromise the well's flow assurance, occurring not only in the wellbore but also in the reservoir pores, reducing flow efficiency and clogging the flow paths. This paper discusses an integrated workflow for determining the root cause of damage in the well. Thus, the remedial strategy can be better defined.

Laboratory testing is crucial to identify the root cause of damage. The integrated laboratory experiments were designed to elucidate, diagnose, and mitigate the damage mechanism. In this study, it was divided into 3 integrated tests: rock solids (inorganic), fluids (organic), and mixtures (wax). The X-ray diffraction (XRD) technique was used to determine mineral compositions of rock. The particle size dispersed in reservoir fluid were measured through dynamic light scattering instrument. The properties and precipitations of organic and mixtures were measured. Water composition and crude oil were analysed and characterized through saturate, asphaltene, resin and aromatic (SARA) analysis.

The colloidal stability index was determined from SARA analysis and considered stable. The composition of water was determined to contain only 20 ppm of calcium carbonate. The wax content, pour-point and wax apparent temperature were measured at 1.61%, 6°C, and 12°C respectively, which was significantly lower than the flowing tubing head temperature. Therefore, the potential damage caused by organic and mixtures deposition can be minimized. This well was being produced from sandstone rock, there was no obvious evidence of sand being produced into the surface, which was consistent with observations from a neighbouring well producing from a similar formation. Sand production was measured around 9-15pptb, which was classified as an obscurely produced sand problem. The mineralogy of the formation has been determined using XRD analysis both from the observed well and a neighbouring well. Both wells demonstrated consistency when the clay content was 20-30% with the major clay type observed as migrating clay (&gt;50%) and minor as swelling clay (&lt;1%). According to particle size analysis of surface fluid samples, the majority (90%) of particles size in both the oil and water phases were less than 2 μm in diameter, which corresponds to the size of clay particles (fines) produced to the surface.

The workflow can identify the root cause of formation damage in this well, which is a mechanical mechanism caused by fines migration. Treatment with a fine stabilizer may be chosen to prolong the productivity of the well. This workflow can be used as a practical guide for determining the source of formation damage via integrated laboratory experiments.