New Method of Improving Formation Evaluation in High-Angle or Horizontal Wells Using Image-Constrained Inversion

Syofyan, Syofvas; Hanif, Muhammad; Latief, Agus Izudin; Gazar, Ashraf Lotfy El; Al-Shabibi, T. A.; Boesing, D.; Deng, Lichuan; Fernandes, Warren; Soliman, Ahmed M.; Smart, Charles R.

doi:10.2118/188795-ms

Cited by 5 publications

(1 citation statement)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Valdisturlo et al (2013) mentioned asymmetric invasion profiles and segregation of drilled cuttings as challenges in the interpretation of resistivity logs in horizontal wells. In addition, Ortenzi et al (2012), Wen et al (2013), and Sun et al (2014 have addressed various issues related to the usage and interpretation of resistivity logs in horizontal wells.…”

Section: Introductionmentioning

confidence: 99%

A review of basic well log interpretation techniques in highly deviated wells

Ghosh

2022

J Petrol Explor Prod Technol

View full text Add to dashboard Cite

Drilling deviated wells has become customary in recent times. This work condenses various highly deviated and horizontal well log interpretation techniques supported by field examples. Compared to that in vertical wells, log interpretation in highly deviated wells is complex because the readings are affected not only by the host bed but also the adjacent beds and additional wellbore-related issues. However, understanding the potential pitfalls and combining information from multiple logs can address some of the challenges. For example, a non-azimuthally focused gamma ray logging while drilling (LWD) tool, used in combination with azimuthally focused density and neutron porosity tools, can accurately tell if an adjacent approaching bed is overlying or underlying. Moreover, resistivity logs in horizontal wells are effective in detecting the presence of adjacent beds. Although the horns associated with resistivity measurements in highly deviated wells are unwanted, their sizes can provide important clues about the angle of the borehole with respect to the intersecting beds. Inversion of horizontal/deviated well logs can also help determine true formation resistivities. Additionally, observed disagreement between resistivity readings with nuclear magnetic resonance (NMR) T2 hydrocarbon peaks can indicate the presence or absence of hydrocarbons. Furthermore, variations in pulsed neutron capture cross sections along horizontal wells, measured while injecting various fluids, can indicate high porosity/permeability unperforated productive zones. Finally, great advances have been made in the direction of the bed geometry determination and geologic modeling using the mentioned deviated well logs. More attention is required toward quantitative log interpretation in horizontal/high angle wells for determining the amount of hydrocarbons in place.

show abstract

Section: Introductionmentioning

confidence: 99%

A review of basic well log interpretation techniques in highly deviated wells

Ghosh

2022

J Petrol Explor Prod Technol

View full text Add to dashboard Cite

show abstract

True Resistivity in High-Angle and Horizontal Wells - Correction of Thin Layer Effects Using Image-Constrained Inversion

Boesing

Wessling

Marsh

et al. 2017

Day 2 Tue, November 14, 2017

View full text Add to dashboard Cite

The application of traditional petrophysical interpretation techniques for formation evaluation (FE) in high-angle/horizontal (HA/Hz) wells is limited because formation geometry affects circumferentially averaged and/or deep-reading logs such as multi-propagation resistivity (MPR). The log responses of neutron-density (N/D) or gamma ray (GR) may not correlate with MPR readings as a consequence of different depths of investigation and azimuthal variation of the lithology around the wellbore. Therefore, alternative approaches and modeling workflows are needed for quantitative petrophysical evaluation of the individual layers. This study on HA/Hz wells demonstrates the benefits of combining different types of FE data for a quantitative petrophysical evaluation in a shale-sand formation using an image-constrained resistivity inversion algorithm. It includes the calculation of true formation resistivity in sand reservoir intervals, with the expectation that intersecting shale layers affect the MPR readings. The increased shale content in the form of thin laminations was indicated on the GR log. To account for the thin and conductive shale layers in a resistivity inversion, a detailed structural earth model was created for the near wellbore. The strike and dip of boundaries were interpreted from a bulk density borehole image and projected away from the borehole within a depth-of-detection tube. The layers in the model were populated with expected property values derived from offset wells and the interpretations of the related FE logs. A resistivity inversion algorithm was run as part of the workflow, providing true formation resistivity (Rt) as output. A synthetic data set was used for demonstrating purposes. The data set consisted of a 70 degree inclined well penetrating horizontally layered sand-shale sequences. The applicability of the new approach was then confirmed by a field data set from the North Sea in which FE data were acquired in a high-angle well using logging-while-drilling (LWD). In both data sets the formation geometry affected the log responses. The workflow described in this study enabled efficient merging of detailed borehole image information into the forward modeling and inversion processes. The true formation resistivity was obtained for each layer for input for further petrophysical analysis using traditional interpretation techniques. The comparison of water saturation calculations based on apparent and on true resistivity logs, respectively, demonstrated the added value of this approach for an improved quantitative petrophysical evaluation and revealed the significant impact of formation geometry effects in HA/Hz wells.

show abstract

Resolving Water Saturation Uncertainty in a Thin Oil Rim Reservoir, Using Sigma While Drilling, Case Study from Onshore Abu Dhabi

Syofyan

Latief

Amoudi

et al. 2017

Day 2 Tue, November 14, 2017

View full text Add to dashboard Cite

Objectives This study focuses on resolving the water saturation (Sw) uncertainty in a small oil rim that consist of thin high-permeability layers (super K). Resistivity-based water saturation techniques suffer from multiple uncertainties including thin layers with distinct capillarity profile, inaccurate resistivity due to high-angle bed effects and unknown Archie parameters. Accurate saturation using alternate methods than resistivity based is critical for the calibration of saturation height model for reserve estimate and to design the perforation program away from the mobile water zone. Methods To resolve the issue of accurate Sw, an alternate method of computing saturation from sigma measurements while drilling is being investigated. Data from multiple wells has been analyzed- saturation from sigma being computed and compared to resistivity based saturation. The resulting saturation is benchmarked against other known sources of saturation like core data and cased-hole measurements. The input parameters used to compute the sigma-based saturation were validated by well test and PVT lab data. Observations A general assumption for LWD logs is that invasion is so shallow that LWD data acquired during drilling may be sufficient to evaluate uninvaded zone properties However, this premise need to be confirmed by other sources of information, in this case Multi-Depth of Investigation (MDOI) sigma data. It provides valuable insight into the status of formation invasion, at the time of acquiring data and of measurement quality control. In situations where the resistivity data does not suffer from any high-angle bed effects, there is immense value in combining the information from resistivity and sigma. When there are two measurements free from invasion and reading the same volume of rock, this can be used for not only calculating water saturations but also to fine-tune the Archie parameters, which might be of immense value in situations, for use on offset wells with resistivity data only. Novel Information Sigma while drilling is another weapon in the arsenal of the petrophysicist and the multi-depth of investigation sigma measurements in a LWD environment contributes a new opportunity to evaluate fluid saturations in reservoirs with unknown or variable Archie parameters.

show abstract

New Method of Improving Formation Evaluation in High-Angle or Horizontal Wells Using Image-Constrained Inversion

Cited by 5 publications

References 3 publications

A review of basic well log interpretation techniques in highly deviated wells

A review of basic well log interpretation techniques in highly deviated wells

True Resistivity in High-Angle and Horizontal Wells - Correction of Thin Layer Effects Using Image-Constrained Inversion

Resolving Water Saturation Uncertainty in a Thin Oil Rim Reservoir, Using Sigma While Drilling, Case Study from Onshore Abu Dhabi

Contact Info

Product

Resources

About