Extending Formation Tester Performance to a Higher Temperature Limit
Authors: Daungkaew Saifon , Yimyam Nitipong , Avant Chris Edward , Hill Jesse , Sintoovongse Kasian , Nguyen-thuyet Alain , Slapal Miroslav , Ayan Cosan , Osman Kamal E. , Wanwises Juntra , Heath Greg Arthur , Salilasiri Sarun , Kongkanoi Chompunoot , Prapasanobon Non , Sirimongkolkitti Awirut , Ngo Hien Quang , Kuntawang Kiatisak 
Published: March 2015

Exploration and development wells are increasingly drilled to deeper depths and lower porosities, in hotter formations. These conditions increase the challenges for Formation Tester's (FT's) to acquire accurate formation pressures in a timely and cost efficient manner. One of the most important constraints on current FT acquisition is the downhole formation temperature. The Pattani and North Malay basins in the Gulf of Thailand (GoT) are known to be one of the highest temperature locations where FT data is routinely acquired. Successful exploitation of the hydrocarbon resources in these basins is strongly driven by cost efficiency and the characterization of the many individual sands that are part of the complex fluvial stratigraphic framework. Reservoir pressure, fluid type, inflow performance and sand-to-sand correlation are some of the objectives for acquiring FT data and are used to manage the many wells drilled each year in these basins. Chevron (Thailand) E&P and PTTEP are the main operators in the GoT, drilling roughly 450 wells each year and over 80% of the wells have bottomhole temperatures in excess of 320 degF. Roughly 80% of the wells drilled require FT logging in the data acquisition program. The main challenge in this high temperature environment for formation testing acquisition is that pressure gauges need to be stabilized to eliminate a transient effect due to high temperature, in order to obtain an accurate pressure measurement. This can lead to longer logging times with the current tools available and lost efficiencies, particularly for wells with many individual hydrocarbon bearing sands (high pay counts).

To improve efficiency and the actual formation pressure management, a proposal was made to develop a High Temperature FT tool in early 2009. This paper discusses the development challenges for FT's in this high temperature area, including gauge selection, gauge limitation, gauge temperature transient effects and logging procedures. After an intensive working period, a specially-made flask to cover certain parts of the tool for heat transfer and mitigation was introduced. Since then, this new FT service has been deployed in more than 20 wells in the Gulf of Thailand. This paper also presents the actual field data from the new tool in terms of data quality and accuracy compared to previous generations of FT, and the resultant efficiency gains from rig time savings. With this development, it is currently possible to obtain accurate formation pressure data, even in the extreme high temperatures found in the GoT, where satisfactory results were not possible in the past.

Introduction

Wireline formation testing measurements are an essential element to define the nature of fluids in place, pressure regimes, and dynamic properties such as mobilities. Exploration and development wells continue to trend towards deeper and hotter formations over time, which challenge and exceed the current generation of FT operating envelopes. There is an increasing need for dynamic FT tools that are fully combinable with other primary logging suites, have reduced sticking probability and can perform in extreme temperature and pressure environments.