Combating Solids Precipitation and Deposition in Adhi Gas-Condensate Process Plant

Ahmed, Shujjat (Pakistan Petroleum Limited) | Qadeer, Suhail (Pakistan Petroleum Limited) | Bouamra, Reda (Schlumberger) | Chaker, Ahmed Abu (Schlumberger) | Jamaiuddin, Abul (Schlumberger)




Adhi gas-condensate field is located near Islamabad, Pakistan. Pakistan Petroleum Limited started fluid processing and recovery of Liquefied Petroleum Gas and Condensate around in 1990. The liquid stream was processed with no solids deposition in the past. Recently, the liquid processing circuit of the plant has experienced an increasing amount of black solid deposition, which is trapped into the liquid filters located in the plant.


To identify the root causes of the problem of these solids depositional systematic approach was applied including taking various solid, liquid and gas samples from the plant inlet and various locations inside the processing plant and analyzing them for diagnostics.


Based on the outcome of the root-cause analysis, a chemical mitigation strategy has been developed, tested and implemented, resulting in significant reduction in problems related with solid depositions in processing plant.




Adhi gas condensate field is located near Islamabad, Pakistan. The fluid in Adhi is processed in two liquefied Petroleum Gas (LPG)/Natural Gas Liquid (NGL) plants (plants I and II) and Oil Stabilization Facility (OSF). The condensate was processed without solid deposition in these plants from 1990 to 2007.


The black solid deposits started to accumulate on the process equipment and plants' filters (Figure-1)leading to a high filter change frequency and consequent production loss.


Due to the continuous increase of the severity of the problem, a full Flow Assurance (FA) review of the field was carried out in order to mitigate the solid precipitation and problem of its depositions in plant. The first phase of the FA review was to conduct a Root Cause Analysis (RCA) where the main causes were identified including fluid compositional changes, temperature and pressure changes across the system, and incompatibility of mixing well streams with different compositions were identified to be the main causes for the asphaltenes dropout.


The RCA was based on the historical plant production data, fluid sampling, analysis results and asphaltene thermodynamic modeling.


The outcomes were:


  • Identification of the root causes.
  • Formulation of a custom solid management workflow.
  • Implementation of robust solution to solve the solid deposition problem.


This article details the methodology followed in solving the solid deposition problem at Adhi.