Reservoir Rock Classification by Comprehensive Petrophysical Data Integration – Acacus Formation, Jenein-Sud, Tunisia

Steckhan, Jan

doi:10.3997/2214-4609.20145787

Cited by 2 publications

(1 citation statement)

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“…With the MICP data as well as the log data a rock-type specific capillary pressure model (Steckhan, 2009) was established to estimate FWL elevations by Leverett J-functions for structures with undrilled fluid contacts and to initialize water saturations in the static and dynamic model at the equilibrium. This paper presents workflow integrating open-hole logging data including GWD, conventional logs, and NMR logs for picking intervals for further examination using WFT.…”

Section: Introductionmentioning

confidence: 99%

A Practical Approach to Determine Low-Resistivity Pay in Clastic Reservoirs

Chu

Steckhan

2011

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Low-resistivity pay (LRP) has been a challenging problem in formation evaluation for many years. This is because conventional petrophysical interpretations are unable to identify pay intervals in low-resistivity reservoirs. This paper lays out a robust workflow for identifying LRP in thinly laminated sands with silty and/or shaly layers.The workflow is essentially a two-step process which integrates data from gas while drilling (GWD), conventional logs and nuclear magnetic resonance (NMR) logs which identify potential pay intervals for further examination using wireline formation tester (WFT). This approach allows one not only to identify pay intervals but also their phase and their flow characteristics without the need of a conventional drill-stem-test (DST).It is common for LRP to have high water saturation (60-70%) computed by conventional petrophysical interpretation while producing sustained water-free oil for few years. A petrophysical study was undertaken to integrate core data analyses including conventional, NMR and mercury injection capillary pressure (MICP). Data from over 100 sidewall cores (SWC) were examined. This novel approach for estimating irreducible water saturation (S wi ) was developed based on 1. A good relationship was recognized between S wi from capillary pressure data as compared to that estimated from NMR de-saturated core. 2. A correlation was established between S wi of de-saturated core and T 2, LM . 3. A validation was performed for zones producing water-free oil to link between NMR-MICP core analysis and NMR logs, using the following two methods for estimating S wi from a. capillary pressure data that is computed with knowledge of the height above free water level (FWL), b. T 2, LM of NMR logs using the correlation developed in Step 2. The benefits of this methodology are that it improves decision in well completion, predicts well performance accurately and reduces uncertainty in reserve estimation. In addition, it allows the user not only to identify zones of pay that would have been missed using conventional analysis, but also to estimate FWL elevations with higher accuracy from a saturation height model (SHM). Saturation profiles derived by this approach and those ones modeled from saturation height equations based on MICP capillary pressure data can be fitted better due to substantial reduction in uncertainties of log derived saturation data. Consequently the initialization of in-place volumes for hydrocarbons will be enhanced.

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Section: Introductionmentioning

confidence: 99%

A Practical Approach to Determine Low-Resistivity Pay in Clastic Reservoirs

Chu

Steckhan

2011

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Development Planning for Multiple Fields Consisting of Stacked Sands and Containing Multiple Fluids, Jenein Sud, Tunisia

Mantatzis

Boisseau

Steckhan

et al. 2010

SPE EUROPEC/EAGE Annual Conference and Exhibition

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The Jenein Sud area is located in the south of Tunisia about 350 km from the Mediterranean Sea. Five successful wells have been drilled in the area and proved that structures containing various fluids are present and can be produced at economic rates. In this paper, the main challenges encountered in the area and how they were tackled is described. Pethrophysical parameters: Owing to diagenetic processes such as chloritisation, siderite cementation and quartz overgrowth, the porosity to permeability relationship is diffuse and cannot be consider for permeability estimation. Therefore, all available petrophysical datasets were integrated and clustered by using an appropriate rock typing concept, reflecting the influence of pore geometries on flow and storage. Sand distribution: Sand layers could not be correlated laterally due to the prograding environment encountered and the large distance between the drilled wells. To capture the uncertainties, a multitude of geological models was created, integrating available seismic data, outcrop studies and trends apparent from regional geology. Fluids: The individual structures consist of a large number of stacked sands. The fluids in the sands vary from dry gas to volatile oil. All the sands have individual hydrocarbon/water contacts. To determine the fluid composition of the layers and overall performance, MDT samples were taken from the sands and several production tests were performed. An overall Equation Of State model was used to describe the comingling of individual sand layers and to optimise the surface facility design. Small scale structures: To appraise the area, wells have been drilled in individual structures rather than appraisal wells into selected structures. The wells are used to prove sufficient hydrocarbons and the composition of the hydrocarbons. This information was used to select an appropriate surface facility design capable of handling the fluids and to optimise the production strategy of the area.

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Reservoir Rock Classification by Comprehensive Petrophysical Data Integration – Acacus Formation, Jenein-Sud, Tunisia

Cited by 2 publications

References 0 publications

A Practical Approach to Determine Low-Resistivity Pay in Clastic Reservoirs

A Practical Approach to Determine Low-Resistivity Pay in Clastic Reservoirs

Development Planning for Multiple Fields Consisting of Stacked Sands and Containing Multiple Fluids, Jenein Sud, Tunisia

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