Novel Integrated Approach for Complex Carbonate Reservoirs Testing with Wireline Formation Tester: Yurubcheno-Tokhomskoye Field Cases Study

In the presented paper, the object of the study are carbonate rocks of the Riphean and clastic-carbonate rocks of Vendian-Cambrian ages, uncovered by the well drilled at Yurubcheno-Tokhomskoye field. These reservoirs are characterized by extremely low porosity (1-4%) and determining saturation nature and fluid contacts cannot be reliably solved by conventional wireline petrophysical logging. Solutions to these problems are provided by interval testing using wireline formation evaluation testing tool (WFT). However, to obtain quality results from WFT testing it is important to identify porous intervals first by using advanced wireline logging services which are sensitive to porosity and fractures. In order to select the optimal WFT toolstring combination and to prospective testing intervals, advanced petrophysical wireline logging suit ran first. Porous reservoirs were identified from density, neutron and nuclear magnetic resonance evaluation. Saturation evaluated through dielectric and induction-based resistivity logging. In fracture-vug type reservoir, the main inflow of formation fluid into the well is provided from fractures, so it was very important to allocate conductive fractures to plan test intervals for WFT accordingly. based on imagers evaluation, fractures and faults were visualized; using Stoneley's wave conductive fractures, not clogged with drilling mud solids were identified; borehole acoustic reflection survey was used to segregate large fractures that propagated in the reservoir; During WFT logging, a total of 23 intervals were tested, for 8 of which reservoir fluid inflow was achieved, in all others, mainly with low porosity or single non-conductive fracture, the inflow was not achieved or was insignificant. According to the results of WFT testing, the nature of saturation for clastic-carbonate sediments of Vendian age was determined. Inflow of formation fluid (oil and water) from Riphean fractured reservoirs was achieved from 6 intervals, with identified fractures according to described above advanced logging suit. In addition, pressure transient analysis was performed, to measure the formation pressure, define pressure gradient curves and assess the fluids contact level with high confidence, for the first time for this field.

Expanding the Capabilities of Modern Wireline Formation Testers for Understanding the Structure of Tight and Fractured Suprasalt Carbonate Field in West Kazakhstan

Low porosity carbonate reservoirs of the Carboniferous and Devonian periods of the Caspian Basin in Western Kazakhstan are challenging to characterize using traditional well logging methods due to the complex structure of the pore space, which necessitates lengthy and sometimes ineffective production well tests. Limitations of standard well logging methods make it impossible to reliably identify productive reservoirs, determine boundary conditions, and delineate saturation. As a result, a unique approach is required, which includes the integration of special "high-tech" logging tools and wireline formation testers (WFT). This paper effectively demonstrates the use of this approach in an appraisal exploration well. The use of a wireline formation tester in conjunction with modern complex fluid analyzers and a radial probe allowed for testing several carbonate intervals with extremely low-permeability in one trip, which previously required stimulation to trigger fluid inflow in a cased well. This provided a new perspective on understanding the reservoir structure in the shortest amount of time possible.

Determination of well spacing volumetric factor for assessment of final oil recovery in reservoirs developed by horizontal wells

The formula for determination of volumetric factor of well spacing for assessment of final oil recovery in reservoirs developed by horizontal wells is offered. For the purpose of comparison of well spacing calculated using conventional and volumetric techniques, twelve development options of the pilot area of the Yamashinskoye field with variousplacement of vertical and horizontal wells were considered. By results of calculations, marked difference in values of well spacing was observed testifying that the conventional formula used to calculate well spacing does not consider the volume nature of fluid inflow to wells with one or more horizontal laterals. The offered technique of volumetric determination of well spacing through the inclination angle, the radius of well drainage area, and the length of a lateral considers the volumetric nature of inflow to horizontal multilateral wells.

Correction to: Earthquake-induced clastic dyke and fluid inflow at the Miguel Burnier manganese-ore deposit, Quadrilátero Ferrífero of Minas Gerais, Brazil

A correction to this paper has been published: https://doi.org/10.1007/s42452-021-04481-z

Earthquake-induced clastic dyke and fluid inflow at the Miguel Burnier manganese-ore deposit, Quadrilátero Ferrífero of Minas Gerais, Brazil

A clastic dyke has been recognised within manganese (Mn)-rich Cenozoic sediments near a historical Mn-ore deposit in the Miguel Burnier district, Quadrilátero Ferrífero, in the southern São Francisco craton, Brazil. Here, we describe the clastic dyke, a subvertical fissure that is filled with friable arenaceous fragments, and characterise it as seismite. An overprint by stockwork-like Mn-oxide veinlets and Mn-oxide dissemination, mineralogically expressed as birnessite, lithiophorite and jianshuiite, and geochemically represented by metalliferous enrichments, particularly mercury (Hg), occurs in the clastic dyke and its immediate vicinity. Such an overprint also contains illite, which forms a mineral association with birnessite, lithiophorite and jianshuiite, and constrains the temperature of hydrothermal alteration to less than 300 °C. The recognition of seismite and its Hg enrichment indicate that the Cenozoic history of the Quadrilátero Ferrífero cratonic terrane has been affected by seismic episodes, which were not only conducive to local enrichment in Mn at Miguel Burnier, but also to recent seismic-related phenomena such as a dam failure (Agurto-Detzel et al. in GRL 43: 4929–4936, 2016).

The effect of seismic deformation mechanisms on fluid migration in accumulation area of gold ore concentrations

This study investigates the effect of mechanisms of paleode formations during the period of fluid inflow into the accumulation sphere of gold concentrations. Such mechanisms are believed to correspond to DC- and NDC- type seismic mechanisms, whose main influence on fluid migration lies on the formation of different, relative to fluid regime parameters, structural and hydrodynamic organizations of the ore-forming system, and fluid flow control within the area of the accumulation of ore concentrations.