Multi-well deconvolution for field start-ups in the North Sea
By Alex Thatcher, Petroleum Engineer, OPC
I was delighted to be asked to present to the SPE Aberdeen section about multi-well deconvolution and its relevance to the North Sea. The most recent licence awards in the North Sea are blocks in mature producing areas close to existing infrastructure. Many were deemed uneconomical to develop in the past but now can be developed as tie backs to the existing infrastructure with few wells. These provide ideal conditions for multi-well deconvolution and we are currently in discussion with a number of operators about providing analysis on their assets. Please get in touch if you want to find out more.
Multi-well deconvolution for field start-ups in the North Sea - presented by Alex Thatcher of OPC
Abstract of webinar
Commonly used deconvolution techniques are a useful addition to the well test analysis toolbox. These techniques are limited to single well pressure and rate data and are therefore more suited to exploration / appraisal testing and certain development situations such as a single well-draining the entire reservoir; a compartmentalized field with one well per compartment; a connected reservoir where the reservoir has dynamically divided into separate drainage areas.
A problem arises when the reservoir is connected but the wells are not operated in a steady fashion which is typical of real field operations. In this case, one must resort to Multi-Well deconvolution analysis. Multi-Well deconvolution converts pressure and rate histories from potentially interfering wells into constant-rate pressure responses for each well as if it were producing alone in the reservoir. It also extracts the interference responses observed at each of the other wells due to this single well production.
Analysis using Multi-Well deconvolution can become complicated for several reasons. Deconvolution requires single phase fluid flow within the reservoir as this technique can only be applied to pressure and rate data represented by linear equations. Additionally, interference pressure signals produced by other wells are small compared to the pressure signal caused by the production of the well itself making them difficult to resolve. These pressure interference signals are delayed in time and the time delay depends on the distance and reservoir properties between respective wells. Hence Multi-Well deconvolution can be a difficult problem when the number of wells is large.
Multi-Well deconvolution analysis may help in understanding the geometry of fluid flow in the reservoir, reservoir connectivity across the field, large scale reservoir heterogeneities and provide estimates of reservoir rock and well properties. It can also yield information regarding the reservoir volume supported by reservoir dynamic pressure and rate data which ultimately drives long term production performance.
The North Sea is now a mature basin with extensive infrastructure. This has and will allow many small fields previously deemed uneconomic to tie into the network. These fields may start life with the reservoir fluid as single phase and may be developed with only a few wells which provides ideal conditions for the application of Multi-Well deconvolution.
Pressure Transient Analysis
OPC specialises in Pressure Transient Analysis (PTA), also known as Well test analysis, which involves the interpretation and analysis of Drill Stem Test (DST), Extended Well Test (EWT) and Production/Injection permanent downhole gauge data.
OPC is one of the leading independent reservoir engineering consultants in the world providing services on a global basis to IOCs, NOCs and independent oil & gas businesses.
Reservoir engineering studies have included phase behaviour and equation of state modelling and production engineering.