Page 407 - Hydrocarbon Exploration and Production Second Edition

394 Managing the Surface Facilities

During production, the ‘health’ of the well is monitored by measuring
production rates – oil, water, gas
pressures – tubing head and downhole
sand production.
From downhole pressure drawdown and build-up surveys the reservoir permea-
bility, the well productivity index and completion skin can be measured. Any devia-
tion from previous measurements or from the theoretically calculated values should
be investigated to determine whether the cause should be treated.
New technology is applied to existing fields to enhance production. For example,
horizontal development wells have been drilled in many mature fields to recover
remaining oil, especially where the remaining oil is present in thin oil columns after
the gas cap and/or aquifer have swept most of the oil. The advent of multilateral wells
drilled with coiled tubing has provided a low cost option to produce remaining oil
as well as low productivity reservoirs.
3D seismic is becoming increasingly used as a tool for development planning,
as well as being used for exploration and appraisal. A 3D survey in a mature field
may identify areas of unswept oil, and is useful in locating infill wells, which are those
wells drilled after the main development wells with the objective of producing
remaining oil.

16.2. Managing the Surface Facilities

The purpose of the surface facilities is to deliver saleable hydrocarbons from the
wellhead to the customer, on time, to specification, in a safe and environmentally
acceptable manner. The main functions of the surface facilities are

gathering, for example manifolding together producing wells
separation, for example gas from liquid, water from oil, sand from liquid
transport, for example from platform to terminal in a pipeline
storage, for example oil tanks to supply production to a tanker.
The surface facilities used to perform these functions are discussed in Section 11.1,
Chapter 11, and are installed as a sequence or train of vessels, valves, pipes, tanks etc.
This section will concentrate on the optimisation of the production system designed
and installed in the development phase. The system needs to be managed during the
production period to maximise the system’s capacity or possible throughput and
availability or the fraction of time for which the system is available.

16.2.1. Capacity constraints
During the design phase, the hardware items of equipment or facilities are designed
for operating conditions which are anticipated based on the information gathered
during field appraisal, and on the outcome of studies such as the reservoir simulation.