Estimating Stratigraphic Parameters from Well Test Data in Turbidite Reservoirs

Well test analysis is a valuable tool to measure the dynamic response of a reservoir through determination of the hydraulic connectivity and effective permeability of the reservoir. Analytical models in well test analysis, are developed based on a simple geological structures, to provide reasonably good approximations for the description and performance of such reservoirs. Nevertheless, most prolific reservoirs such as channelized systems consist of sedimentological features with high degrees of heterogeneity that influence the pressure transient response where using conventional analytical models may result in misleading interpretations. The focus of the current study is on reservoirs which depositional environment corresponds to a main channel feature incising into heterolithic beds in lateral continuity. Analysis of the pressure response demonstrated that it can be used as a tool to predict the equivalent isotropic horizontal permeability of the channel. We explored that the ratio of well test permeabilities between the radial flows can lead to the identification of a secondary geological body next to channel. Thus, it can be used to find the distance of the interface between channel and heterolithic. The results of this study showed that particular features of pressure and its derivative curves from a channel-heterolithic system are useful well testing signatures for reservoir characterisation. Therefore, we proposed an algorithm for the recognition of pressure trends and the development of relationships to be used for well test interpretation of heterogeneous oil and gas reservoirs.

show abstract

“…0.39m × 0.39m). Local grid refinement is performed to produce accurate well test profiles (Chen et al, 2012).…”

Section: Impact Of the Fine-gridding In Simulation Resultsmentioning

confidence: 99%

Geological interpretation of channelized heterolithic beds through well test analysis

Osório

Haddad

Stephens³

et al. 2017

Journal of Petroleum Science and Engineering

View full text Add to dashboard Cite

show abstract

“…In wells B, C and D, the ¼ slope straight line in the pressure derivative starts earlier and further investigation is required. Chen et al (2012) suggested that the complexity of the depositional environment in turbidite reservoirs cannot be estimated using conventional analytical models but can be captured by numerical simulation of the well test. In this study, a systematic methodology for numerical simulation of the well test analysis was followed: …”

Section: Transition Effect Of Characteristic Flow Regimesmentioning

confidence: 99%

“…Now that it is established that there are no barriers between the horizontal wells from the modified pulse tests and possible areal anisotropy, plausible geological features in the reservoir that may lead to a bilinear flow regime can be modeled. In turbidite reservoirs, the degree of amalgamation, dimensions of lobe size, channel width, flow barriers in the form of cemented gravel lags or shale drapes and their coverage may affect well test data (Chen et al, 2012). The following geological features were modeled and its pressure behavior analyzed:…”

Section: Base Model Construction and Verificationmentioning

confidence: 99%

Bilinear Flow in Horizontal Wells in a Homogeneous Reservoir: Huntington Case Study

Feng

2015

Europec 2015

View full text Add to dashboard Cite

In the Huntington field, bilinear flow with a clear one-quarter unit slope in the pressure derivative has been observed during intermediate-times in horizontal well tests, instead of the usual linear flow with a half unit slope expected in a homogeneous reservoir. This paper investigates various analytical methods with numerical methods to explain this behaviour.A number of plausible explanations of this pressure behavior were investigated in this study: rate history or production-time effects; transition between early and late time derivative radial flow stabilizations which could yield a quarter slope straight line on the derivative for specific combinations of horizontal and vertical permeabilities, well length and reservoir thickness; and geological conditions such as high-permeability streaks, the presence of shale barriers, and layering with varying permeability.It was concluded from numerical simulations and geological evidence that the most likely explanation, which yields the best match with well test data, was uniform horizontal permeability and non-uniform vertical permeability increasing from the bottom to the top of the reservoir. This is consistent with the geology of the Huntington field, where the depositional sequence is dominated by high-density turbidity currents.At each sedimentation pulse, heavier pebble/gravel lags were deposited first at the base of channels followed by finer particles which may have formed thin shale drapes. In addition, diagenesis might have led to cementation of pebble/gravel lags. The non-uniform and non-laterally extensive occurrence of the cemented pebble/gravel lags and thin shale drapes act as local baffles to vertical flow but not to horizontal flow resulting in bilinear flow behaviour in the reservoir. This paper offers a unique insight into an integrated effort at combining analytical, numerical well test models and geological evidence to explain the reservoir behavior observed in the Huntington field.

show abstract

“…The backbone-cluster type of flow has been observed in laboratory experiments (Klemm et al, 1999). A turbiditic system (Chen et al, 2012) with communicating channels and appended lobes may also be approximated by the BB-SC description -in this case with different properties.…”

Section: Percolation Clustersmentioning

confidence: 99%

Pressure Transients in a Fractal-Cluster Model of Porous Media

Swaan¹

2014

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

View full text Add to dashboard Cite

-The reservoir is described as a "supercritical cluster"; that is, an aggregate of conductive elements that comprises a "backbone" of connected pores or fractures that span the zone of interest, and also a collection of "sub-critical clusters" or "dangling ends" joined to the backbone to a limited extent. The scheme resembles the usual fracture and matrix-blocks setting but both backbone and sub-clusters are of the same material and share similar petrophysical properties. Whereas the backbone is a homogeneous porous medium, the sub-critical clusters behave as fractal porous media. The backbone-cluster type of flow has been observed in laboratory experiments. The subcritical clusters were approximated as linear fractal media characterized by static and dynamic fractal exponents and also by porosity and permeability of the compound medium. One of the ends of the linear clusters is closed and the other is joined to the backbone, where the mainstream occurs. A new solution was developed for that problem. The Laplace transform in time and space was used in the mathematical scheme. The theory developed was applied to field cases of interference between wells in aquifers. The matches of computed and observed dynamic pressures show fair fits.Re´sume´-Transitoires de pression dans un mode`le d'agre´gat fractal de milieux poreuxLe re´servoir est de´crit comme un « agre´gat supercritique » ; a`savoir un ensemble d'e´le´ments conducteurs comprenant un « squelette » de pores connecte´s ou de fractures qui s'e´tendent sur la zone d'inte´reˆt et e´galement une collection « d'agre´gats sous-critiques » ou « d'extre´mite´s non sature´es » jointes au squelette sur une distance limite´e. Le sche´ma ressemble a`la fracturation et aux assemblages blocs-matrice habituels mais le squelette et les sous-agre´gats sont du meˆme mate´riau et partagent des proprie´te´s pe´tro-physiques similaires. Tandis que le squelette est un milieu poreux homoge`ne, les agre´gats sous-critiques se comportent comme des milieux poreux fractals. Ce type d'e´coulement a e´te´observe´dans des expe´riences de laboratoire. Les agre´gats sous-critiques ont e´te´repre´sente´s comme des milieux fractals line´aires caracte´rise´s par des exposants fractals statiques et dynamiques et e´galement par la porosite´et la perme´abilite´du milieu du compose´. Une des extre´mite´s des agre´gats line´aires est ferme´e et l'autre est relie´e au squelette, ou`coule le flux principal. Une nouvelle solution a e´te´de´veloppe´e pour ce proble`me. La transforme´e de Laplace dans le temps et l'espace a e´te´utilise´e dans le de´veloppement mathe´matique. La the´orie de´veloppe´e a e´te´applique´e aux cas d'interfe´rence sur le terrain entre les puits dans des aquife`res. Les comparaisons de pressions dynamiques calcule´es et observe´es pre´sentent des re´sultats compatibles.

show abstract

Estimating Stratigraphic Parameters from Well Test Data in Turbidite Reservoirs

Cited by 5 publications

References 9 publications

Geological interpretation of channelized heterolithic beds through well test analysis

Geological interpretation of channelized heterolithic beds through well test analysis

Bilinear Flow in Horizontal Wells in a Homogeneous Reservoir: Huntington Case Study

Pressure Transients in a Fractal-Cluster Model of Porous Media

Contact Info

Product

Resources

About