An emerging technology called sourceless well placement and logging (without using traditional chemical radioactive sources) has intensified in recent years because of various factors, such as drilling risk reduction and cost optimization, as well as evolving government regulatory and health, safety, and environment (HSE) requirements. Established technologies, such as acoustic sensors, have been tested during pilot projects in several Middle Eastern development environments to evaluate the viability of replacing conventional density-neutron sensors. Current developments and integrated workflows are encouraging for the provision of sourceless well placement, porosity, and petrophysical and geomechanical evaluations for some of the mature reservoirs. These developments include a substantial number of case histories already established in clastic and carbonate depositional environments for the previous five years. The current well was planned through carbonate and clastic sequence as part of a geological section deemed important from a borehole stability point of view. Borehole deterioration and significant variations in pore pressure were also considered to increase the potential risk for the drillstring sticking. Conventional porosity tools used during a logging while drilling (LWD) bottomhole assembly (BHA) with radioactive sources exacerbate the potential risk at an environmental-hazard level. Additionally, retrievable-based sources can be problematic during extraction in high-angle wells. LWD azimuthal-acoustic tools free of radioactive sources were run for porosity measurements, pressure prediction, geomechanics, and possible anisotropy using a centralized four-axis acoustic caliper. A comprehensive petrophysical interpretation was also performed as part of the horizontal build section using acoustic porosities in comparison to its nuclear counterparts acquired in different modes. Permeability was deduced from acoustic and high-resolution microimaging data. This paper discusses the planning, design, and use of acoustic tools as part of the BHA and the viability, integrity, limitations, and reliability of logged data and interpreted results. The integration of petrophysical data with cutting analysis is investigated to optimize real-time drilling operations and petrophysical data acquisition requirements for improvement of future developments and overall reservoir management strategies.

This paper presents a multidisciplinary data integration in order to predict tarmat and heavy oil in Minagish Field. Techniques to detect tarmat are divided into those using logs and those which analyse the composition of oils such as Iatroscan geochemical technique; the later is very useful in detecting tarmat because of the remarkable difference in composition of oils in tarmat compared with the overlying reservoir. The second technique used is the pyrolysis method which detects mobile (Sr+S2a+S2b) and immobile (residual carbon RC) hydrocarbons along with TOC. It aids in identifying the nature of hydrocarbons within the pore structure defined by petrographic studies using polarized microscope and SEM. The samples were screened and analyzed using Rock Eval-reservoir methods in order to identify heavy and light hydrocarbon zones. The pyrolysis results show that there are many intervals of heavier oil intercalated with lighter oil ones. The previous studies of Minagish oil showed that this reservoir is richest in heavy polar compounds (26%) compared to other cretaceous reservoirs in Kuwait. Using the above methods, a new model is conceived with a clear variation in oil homogeneity vertically as well as laterally within the reservoir. In addition to that, faults and biodegradation near the water zone played their role in increasing density of oil and forming heavy oil in the reservoir. Application of magnetic resonance image and chemostratigraphic data are found effective in identifying heavier oil, light hydrocarbons and tarmat in real time mode. The chemostratigraphic interpretation draws certain depositional and/or diagenetic facies with definite elemental signatures. High P and P/Mn ratios are associated with oolite grainstones lithology that have high initial porosities and higher tar content. Also, tarmat is recognized by highly elevated values of Ni, V and S. This study led successfully to explain the production of an incremental volume of heavy oil trapped behind the injector in northeast area of the field.

The Cenomanian Wara Formation in Minagish Field is composed mainly of coastal plain deposits, observed at field scale along with shallow marine shales and carbonate bioclastic sandy beds. They are locally disrupted by embedded channelized sandy bodies from fluvio-tidal origin. The reservoir units are represented by different channel geometries with limited areal extension. The placement and completion of horizontal and highly deviated wells in such reservoir is a challenge necessitating a collaborative approach to avoid major well bore instability issues. These issues have a significant impact on the well cost and time line. In addition, having the right placement and completion is important for optimizing the drainage contact. To address such challenges during the different stages of the drilling operation, different technologies were used. For example, while the well was drilling through the unstable Wara and Ahmadi shaley formations, a Logging While Drilling (LWD) sonic and gamma ray (GR) tools were used to update in realtime a predrill geomechanical model with the formation acoustic and GR properties. Having such measurements allowed calculating the right mud weight density which resulted in drilling a stable borehole. This was confirmed by the absence of cavings and tight spots thought out the whole operation. On the other hand, the drain section was drilled in Wara channel sands which are known to be composed of a thinly bedded faulted sand-silt sequence with the sand layers being relatively radioactive. To help steering in such complex environment, a combination of LWD tools were chosen to place the well in the sweet spot of the target. These tools involved using the advanced deep azimuthal resistivity (geosteering) and the Multi-Function LWD (advanced petrophysics) tools. As a result of this, the horizontal section was proactively geosteered in the reservoir in which 1049 ft MD were steered in the high-quality sand layers.

The Minagish Oolite is one of the main reservoirs in the Minagish Field, Southwest Kuwait. The field is a large 4-way dip closure anticline structure, covering an area of about 90 square kilometers and with around 900feet of carbonates of the Minagish formation. The Middle Minagish member is the main reservoir, consisting of oolitic limestone with high permeability in the range of 10 to 1000 mD. The Lower Minagish member contains dense fine grained wackestones to packstones with low permeability. The Middle Minagish and Lower Minagish oil reservoirs contain highly undersaturated oil with API gravities of 28-34 °API and share a common FWL at 9950feet TVDSS. The dynamic model built along with time lapsed historical (production/injection) and well surveillance (PLT, TDT, well test) data are used for tracking the movement of injected water and gas, monitoring fluid contacts and changes in saturation with time, optimizing production and planning of new wells. Nonetheless, due high density of producers existing around the field causes mutual interference amongst the neighboring wells and surprises arise while drilling new wells. Real-time Geochemical analysis on elemental and mineral concentrations within drill cuttings/core chips, integrated with advanced mud gas data, can provide an additional analytical dataset to assess reservoir depletion and water encroachment. This advanced surface logging technology can give a better indication on water bearing zones and water encroachment when MWD/WL logs have resolution issues. When geochemical and mud gas proxies are integrated with other data sets (viz. logs, and dynamic data), they provide a better control on lithological changes and water bearing zones, throughout the entire reservoir. Integrated geochemical and advance mud gas analysis in depleted Minagish reservoir has helped to confirm zones of interest and to determine leading edge of water aquifer. Ultimately this enabled for a unique completion design. The well MN-X, object of the study, represents a valuable case where it has been possible to identify water encroachment through geochemical proxies, aiding the completion strategy.

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