Early Field Life Interference Pulse Test Design to Refine Reservoir Uncertainties: A Reservoir Surveillance Opportunity for the Wheatstone Gas Field, Australia

SPE/IATMI Asia Pacific Oil &Amp; Gas Conference and Exhibition

et al. 2017

In this short technical note we lay out an analytical framework to assess the impact of transient temperature changes in the wellbore on pressure transient response of cold water injection wells. We focus attention on the falloff period of an injector following injection. Historically, these pressure data have been used to calculate reservoir properties concerning flood efficiency and completion properties, e.g.: formation permeability-thickness, mechanical skin and fluid bank mobilities. One key question addressed in this paper is whether the effects of thermal heating of wellbore fluids during a falloff survey can mask the pressure signature of a two-zone composite reservoir. The pressure deflections required to detect mobility changes may be relatively small compared to pressure changes induced by temperature effects in the well. The framework proposed in this paper allows for the numerical evaluation of the contribution of each. Previously, researchers have studied multiple bank transient injection problems extensively for the case of reservoir flow and pressure drop, even for non-isothermal problems. The effect of temperature changes in the wellbore and overburden are seldom discussed, however. It is demonstrated in this paper that these effects can, in some cases, be substantial and it is worthwhile to incorporate them into an interpretation model. The results of this paper are useful for planning and designing a pressure falloff survey to minimise the adverse effect that heating of wellbore fluid by overburden rock may have on the pressure transient signature. The theory can also be used to analyse existing data affected by the phenomenon.

Pressure Transient Analysis for Cold Water Injection into a Reservoir with a Coupled Analytic Wellbore Model

O'Reilly

Haghighi

SPE/IATMI Asia Pacific Oil &Amp; Gas Conference and Exhibition

et al. 2017

Pressure-Transient Analysis for Cold-Water Injection into a Reservoir Coupled with Wellbore-Transient-Temperature Effects

O'Reilly

Haghighi

SPE Production &Amp; Operations

et al. 2020

Summary Presented here is an analytical framework to assess the impact of transient-temperature changes in the wellbore on the pressure-transient response of cold-water injection wells. We focus attention on both drawdown and falloff periods in a well after injection. Historically, these pressure data have been used to calculate reservoir properties concerning flood-efficiency and completion properties (formation permeability/thickness, mechanical skin, and fluid-bank mobilities). One key question addressed in this paper is whether the effects of thermal heating of wellbore fluids during a falloff survey can mask the pressure signature of a two-region composite reservoir. The pressure deflections required to detect mobility changes can be relatively small compared with pressure changes induced by temperature effects in the well. The framework proposed in this paper allows for the numerical evaluation of the contribution of each. Previously, researchers have studied multiple bank-transient-injection problems extensively for the case of reservoir flow and pressure drop, even for nonisothermal problems. The effect of temperature changes in the wellbore and overburden are seldom discussed, however. It is demonstrated in this paper that these effects can, in some cases, be substantial, and it is worthwhile to incorporate them into an interpretation model. The results of this paper are useful for planning and designing a pressure-falloff survey to minimize the adverse effect that heating of wellbore fluid by overburden rock can have on the pressure-transient signature. The theory can also be used to analyze existing data affected by the phenomenon. A real-field case study is shown for a cold-water injector where pressure-falloff data have been affected by temperature changes. The analytical model fits the field data closely when parameters are adjusted within reservoir-property-uncertaintyranges.

Application of Ensemble Variance Analysis in the Development of the Wheatstone Field Startup Strategy

SPE Asia Pacific Oil and Gas Conference and Exhibition

Connell

2018

Commencement of initial field production is a unique opportunity to acquire reservoir surveillance information that can inform future reservoir performance. When a field is perturbed from original conditions with first production, there is potential for reservoir property uncertainty reduction by observing pressure measurements at non-producing wells with downhole pressure gauges and comparing the observed signal to a range of simulation model results. The Wheatstone field, located offshore northwest Australia, has recently commenced production start-up to supply gas to the Wheatstone LNG facility. The operational guidelines required each development well to commence with a single well cleanup flow to the Wheatstone platform. The initial single well cleanup flows of the Wheatstone field allowed scope for the selection of a well flow sequence with observation at non-producing wells. The recommended sequence of initial cleanup flows was designed with a focus on reducing reservoir uncertainties via the use of Ensemble Variance Analysis (EVA). EVA is a statistical correlation technique which compares the co-variance between two sets of output data with the same set of inputs. For the Wheatstone field well cleanup flow sequence selection, the EVA workflow compared the full field Design of Experiments (DoE) study of field depletion and a series of short early production reservoir simulation DoE studies of the gas field. The co-variance between the two DoE studies was evaluated. The objective of the EVA approach was to determine the startup sequence that would allow for the best opportunity for subsurface uncertainty reduction. This objective was met by ranking multiple cleanup flow sequence scenarios. The key factors considered for sequence selection ranking were the impact on business objectives such as future drilling campaign timing and location of infill wells, as well as insights on reservoir connectivity, gas initially in place and permeability. The recommended sequence of well cleanup flows uses super-positioning of pressure signal to boost response at observation wells, which improves measurement resolvability. The selected sequence preserves key observation wells for each manifold and reservoir section for as long as possible before those wells were required to be flowed to meet operational requirements. Operational constraints and variations of the startup plan were considered as part of the evaluation.