Development of an Integrated Production Network Model for the Heera Field
Authors: Nadar M. S. , Kulkarni R. , Lemanczyk Z. R. , Aggarwal P. 
Published: December 2007

This paper describes the development of an integrated production network model for a major producing field located in the Western Offshore Region of India, the second most prolific oil field in India.

The purpose is threefold: a) presentation of a case history describing successful implementation of optimisation methodology in a major gas lifted field, b) outlining the structure and methodology for constructing and calibrating a large integrated production model, and c) illustrating the potential applications in running the completed model in optimisation mode.

The Heera Field, currently producing from 119 strings (all on gas lift except one) has been on production since 1984 and with recovery in the region of 20% considerable potential still exists for improving production and recovery. One of the areas and challenges for improvement involves the optimisation of the gas lift performance. The Heera network model described in this paper includes the multi-phase well production, gas lift injection, production processing and gas lift compression facilities that comprise the asset.

The development of the network model comprised the following elements:

Well models were constructed for all the producing strings using nodal analysis. Outflow performance was calibrated to existing flowing gradient survey (FGS) data and recent production test data. Fluid properties were characterized based on Black Oil correlations using four independent PVT datasets, and tuned to a single correlation across the entire field. Approximately 450 independent pipe/flowline objects were included in the model to represent major pipelines, risers and downcomers. Three major processing platforms, comprising 5 HP separators, MP and LP separators, and 5 gas lift compressors operating in parallel were modelled. Production from neighbouring complexes (Neelam and ICP) was included in the form of "object sources" with overall delivery point at the Uran terminal located onshore.

The network model was built, history matched and calibrated to actual field data, within a tolerance of &lt;1% for the measured liquids production. The calibrated model was then used to run a number of optimisation scenarios, in an effort to find ways of improving production and operating efficiency.

Optimisation investigations conducted within the framework of this project indicate potential oil uplift of between 6-8% from a combination of well interventions (based on individual well modelling and gas lift diagnostics) and network optimisation (lift gas reallocation), as well as a reduction in total lift gas requirement and compressor horsepower.

Besides the scope for production gains and operational improvements, the project also highlights a number of higher level issues relevant to the development and employment of integrated production network models:

The successful implementation of the Heera network model is the first of its kind in ONGC's India operations. The technology utilised in this project is capable of modelling large scale complex production networks in a robust and reliable manner. Complexity and size need no longer be barriers to successful implementation of network modelling and optimisation. The technology is easily transferable for implementation by production engineering and operations staff in the field, provided standardised workflows are identified and new work practices implemented to allow improved data management and model maintenance. The maintained integrated production network model provides a platform for analysing and diagnosing a wide variety of production and equipment related issues in the field.

Recommendations from the model are currently being implemented in the field. Based on the modelling recommendations, well interventions and lift gas reallocation have so far produced oil production increases in the region of 1700 BOPD.