TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAs production logging technology advances, more confident results are achieved in multiphase horizontal wells. There are a number of wells with unfavorable completions for production logging. In addition, operational difficulties are observed from time to time posing challenges. In any case, confidence in the determination of fluid entry intervals is required. Because of dynamic data acquisition, real time decisions are needed.

The drilling of development wells in sand stringers involves very thin and sinuous targets. These targets are the channel sand stringers and contain a substantial amount of hydrocarbons. Optimal well placement is a requirement for these very thin reservoirs in order to drain them in a cost effective manner. Conventional well placement has met with limited success in stringers and the production can be expected to be low from these stringers. A technology driven approach of detecting the formation changes early during drilling was needed. These changes, when addressed, can be translated into maximizing reservoir contact, limiting well-bore tortuosity thus enhancing optimal production. Due to the uncertainty that is inherently present in the distribution of the channel sands, the prediction of the azimuth of channel meander can now be confidently solidified with new deep and directional electromagnetic measurements (EM) tool. This is a technology which uses directional EM through the use of tilted and transverse current-loop antennas. By detecting the upper and lower conductive shale boundaries the wells have been steered in this very challenging environment of channel sands. This technology has proven to be a major success in the development of the sand stringers by improving the Net to Gross ratio by more than 50% and hence the longevity and producabilty of the stringer wells as compared to conventional well placement LWD techniques. Introduction Fluvial channels are an important petroleum exploration target in many basins due to their high sand quality and excellent hydrocarbon trapping mechanisms. One way to achieve higher recovery factors in such reservoirs is to increase reservoir contact by drilling horizontal wells. Horizontal well placement in such an environment is challenging due to the changes in reservoir thickness and sand body orientation. To meet this challenge, it is critical to understand the shape of such bodies and the features associated with such depositional system. Flowing rivers in fluvial environments deposit sands in different ways depending on several factors such as stream gradient, consistency of discharge rate, transported sediment grain size, type of the scour surface, the effects of vegetation and natural levees. Depending on these factors we can have different types of fluvial deposits. Recent development drilling operations in Saudi Arabia involve targets near the flanks of the main structure. In last few years a number of wells have been drilled using the newly developed well placement technologies and significantly better net to gross ratio were achieved. The objective of this paper is to share the results of advance well placement process using new technology and its application in main clastic oil fields of Saudi Arabia. Geological Setting The reservoir is thick sequence of quartz-rich sand stones, siltstones, shale and various types of ironstones (siderite, chamosite, and glauconite).

Wireline formation testing provides formation pressures, high quality samples and fluid identification/characterization. In addition, it can provide information for reserve assessment and producibility estimation. In this paper, we present comprehensive formation evaluation case histories with formation testing utilizing a focused sampling probe in wells drilled with Oil Base Muds (OBM) in mature fields. Due to OBM and low mobility sections, a new focused sampling device was utilized for effective formation testing and sampling purity. One case history demonstrates confirming remaining oil saturation. Conventional open hole and Nuclear Magnetic Resonance (NMR) logs were run for formation evaluation, and fluid saturations. Gas and remaining oil saturation were obtained from 3D NMR analysis. Sampling lab results and real time analysis of gas compositions are also compared for verification and confidence. Two field examples in low porosity/low mobility zones are presented showing the identification of mobile fluids. It is shown that the existence of mobile oil could have been missed without effective formation testing practices. The third field example of formation testing with low porosity as well as low resistivity is provided for the identification of mobile oil. Flow was enabled from low mobility zones along with low rate pumpout that would not be possible with traditional probe and pumpout devices. The final field example of water sweep evaluation in high permeabilitiy/mobility zones demonstrates using formation testing as a means of reservoir monitoring. Introduction Recent advances in wireline formation testers enabled the determination of several fluid properties, including fluid compositions in real time. The applications of wireline formation testing has been discussed in a number of publications concerning Downhole Fluid Analysis (DFA)1–4. It has been shown that compartmentalization and compositional variation can be positively identified. This evaluation can have significant impact on facility sizing and economics of field development of new reservoirs. In addition, mini-DST or Interval Pressure Transient Testing (IPTT) can be carried out at DFA stations to provide more representative and accurate mobility/permeability distributions of reservoir layers5 for reservoir characterization. Mature reservoirs can have different objectives and challenges for efficient formation evaluation and reservoir management. As gas cap expands and active aquifer water moves in heteregenous systems, formation pressure profiles can be more complicated. Evaluation of saturations/remaining oil determinations becomes quite important for the determination of sweep efficiency in mature reservoirs. Low porosity/low permeability sections can be more challenging to evaluate and these sections can still have considerable hydrocarbon potential. Although, OBM can be challenging for contamination quantification during sampling operation, it has been shown that optical spectroscopy can be quite effective to overcome contamination challenges6. The challenge can be much more in the case of determining small amounts of mobile oil in a gas expanded zone, drilled with OBM. A focused sampling device is introduced to overcome this challenge by isolating small amount of filtrate that can mix with sampling line. Lab results of the first field example demonstrated that these objectives were achieved.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWireline formation testing provides formation pressures, high quality samples and fluid identification/characterization. In addition, it can provide information for reserve assessment and producibility estimation.In this paper, we present comprehensive formation evaluation case histories with formation testing utilizing a focused sampling probe in wells drilled with Oil Base Muds (OBM) in mature fields. Due to OBM and low mobility sections, a new focused sampling device was utilized for effective formation testing and sampling purity. One case history demonstrates confirming remaining oil saturation. Conventional open hole and Nuclear Magnetic Resonance (NMR) logs were run for formation evaluation, and fluid saturations. Gas and remaining oil saturation were obtained from 3D NMR analysis. Sampling lab results and real time analysis of gas compositions are also compared for verification and confidence.Two field examples in low porosity/low mobility zones are presented showing the identification of mobile fluids. It is shown that the existence of mobile oil could have been missed without effective formation testing practices.The third field example of formation testing with low porosity as well as low resistivity is provided for the identification of mobile oil. Flow was enabled from low mobility zones along with low rate pumpout that would not be possible with traditional probe and pumpout devices.The final field example of water sweep evaluation in high permeabilitiy/mobility zones demonstrates using formation testing as a means of reservoir monitoring.