It is very challenging to measure formation pressure in the low mobility formations of Eastern Desert, Egypt. The measured mobilities ranged from 0.01 to 5 mD/cP; making the acquisition of reliable formation pressure with conventional pretesting very difficult. Many pretests end up being recorded as ‘Dry’, ‘Tight’ and ‘Supercharged’. However, by exploiting the extreme limits of new generation formation testers such as low volume and relatively lower rates, we were able to overcome these difficulties and record valuable formation pressures. The electromechanically controlled formation tester is specifically engineered for only pressure and mobility testing as opposed to multifunctional formation tester tool that also collects samples. The two important distinctions of this tool are an electromechanically controlled pressure pretest system that enables precise pretest volume and rate. This is in contrast to the hydraulically driven pretest mechanisms in conventional tools. Secondly, because the tool is devoted only to pretesting, it has a very small flowline volume with very tight mechanical construction. The required decompression volume is much smaller than conventional tools, brings new efficiency to the formation pressure testing process by significantly reducing both the time and risk involved with wireline formation testing operation. The operating guidelines is prepared to recognize pressure measurement challenges in low mobility formations, it may assist engineers to identify the problems and take corrective measures by altering pretest volume and rate. Correct practice of taking right volume and rate may bring value to pretests whereas inexperience of pressure measurement in low mobility formations may cause significant damage to the data quality. Herein we have presented examples of good quality pretests changing into ‘Dry’ or ‘Tight’ by taking high volumes and also conversely the ‘Dry’ or ‘Tight’ pretests converting into good quality by optimizing pretest volumes.

The Arta fields of Egyptian Eastern Desert are operated by Petrodara, a joint venture of Transglobe Energy and Egyptian General Petroleum Corporation (EGPC). The main producing horizon is the Nukhul and formation pressure measurements are critical in this poorly sorted conglomerated marl in order to understand and model depletion. However, low permeability and high viscosity oils contributed to a very low mobility environment that presented considerable challenges to Wireline Formation Tester (WFT) tools. Extensive testing programs resulted in an excessive amount of tests that were unusable, being classified as ‘dry’, ‘tight’ or ‘supercharged’. This low mobility environment also complicated the requirement for PVT samples acquired with the WFT tools. Normal testing operations resulted in very high drawdowns that sampled below formation pressure and caused emulsions with the filtrate of the water based drilling fluid. In this paper we discuss how the Operator and the Service Company combined to employ fit for purpose WFT techniques to acquire accurate formation pressure data and PVT quality oil samples. Most of our discussion will be based on understanding the dynamics of pretesting in low permeability formations and how the optimal tool and pretest design can produce results where previous attempts have failed. Specifically we consider the newest ‘pretest only’ WFT that provides very fine control over pretest rate and volume and allows precise test design that is not possible with conventional WFT tools. Additionally, we demonstrate the application of best practices and lessons learned from worldwide sampling operation to acquire PVT quality heavy oil samples.

Well A, encountered multiple depleted reservoir layers (initial reservoir pressure >10840 psi) with up to 5,000 psi differential pressure across layers due to irregular depletion in thin bedded shale and sand layers. Well was drilled with over 16 ppg mud to limit under balance in any higher pressure layer and overbalance in depleted layers. After drilling 4 lopes of sand body and during the start of drilling the last sand lope, complete loss of circulation was encountered, followed by kick and differential sticking. The original well integrity assurance plan considered the deployment of borehole compensated sonic tool in order to acquire a discriminated cement bond log based on attenuation measurement. Also in the plan, a Cased Hole Dynamic Tester tool was to be run and the selection of pressure points to be based on the results of the cbl-vdl. So to assure the full integrity of the cement and be able to conduct the Cased Hole Dynamic Tester as required and proper decision to be evaluated regarding the Type of GP job, the use of the Ultrasonic Imaging Tool was evaluated to be run under tough and challenging conditions (high mud weight and thick wall thickness). The Ultrasonic tool for cement to casing bond evaluation is typically limited by the attenuation of the ultrasonic echo caused by the wellbore mud weight and composition. With the cooperation between BP PhPc and Schlumberger, and making use of worldwide expertise, the decision was taken to include the Ultrasonic Tool in the cement evaluation suite despite the well conditions. The analysis of the log managed to prove the zonal isolation requirements and be a source of development of best practices that can improve cement evaluation even with the presence of heavy SOBM.