December 1998 Vol. 219 No. 12  Production

Perry A. Fischer,  Engineering Editor

New production logging tool; Are we awash in LNG?

A new logging tool promises to illustrate almost any downhole production situation. If you have not heard about Schlumberger’s PS Platform production tool, you must have been hiding. The company intends to shorten product cycle time by conducting an en masse campaign to publicize and offer the tool, and establish dedicated service centers worldwide for its new, maximized production (MaxPro) logging service.

Capabilities. Fortunately for clients, the new tool appears to be worth all the hype. Included is a redesigned fullbore spinner, gamma ray, collar locator, fluid density, temperature and pressure sensors; while additions include an optional quartz pressure gauge (0.01 psi resolution), independent X-Y caliper measurements, bubble count and size measurement, percent water holdup calculation and the ability to run the tool in real time or memory mode. Reduced rathole is allowed since the most important measurements are colocated only 16 in. from the tool’s bottom.

Much shorter. The older version of this tool was 28-ft long and offered less capability. The last time this editor ran production logs, extra weights and tool length were important concerns, especially under high pressure, where the need to add a few weights could create an unworkable rig-up height. Being much shorter, and with so much electronics crammed into its 1.69-in.´ 18.5-ft profile, the tool is a little denser, thus requiring fewer additional weights.

New weights. Aside from adding unwanted height, weights have been a significant, albeit unlikely, source of failures. Clients and wireline engineers alike have been disappointed by their occasional failure to perform a simple task: transmit electricity through a single conductor, which is all that is required of weights. A new, slip-over weight system eliminates the need to pass current, thereby excluding a source of failure. Flexible joints and rollers were added at each weight’s end to help reduce friction for improved access in highly-deviated wells.

To read how this technology worked in the real world, see World Oil’s reservoir management issue next month. On a platform built to earlier water-discharge standards, operator Total tells a story of complex production problems that were identified and solved in Dunbar field in the North Sea.

Awash in LNG? You have probably already heard about the predicted oversupply of LNG — a recent U.S. Energy Information Agency (EIA) report arrived at the same conclusion. This conclusion was expected, given the Asian economic crisis and its effect on consumption. Also, construction of a proposed gas pipeline from Sakhalin Island and / or Eastern Siberia to Japan and South Korea — the world’s two largest LNG users — could further soften LNG demand.

Economics of scale requires that giant gas fields are needed, in the several Tcf range, to justify the billions-of-dollars investment in processing facilities, storage, shipping and offloading facilities associated with LNG production. However, new technologies for LNG conversion may soon allow smaller gas fields to be profitable.

Currently, about 4.4 Tcf of LNG is produced each year. Another 1.1 Tcf of capacity is under construction. Add to that another 2.6 Tcf from planned LNG plants, and the oversupply scenario seems reasonable.

Insofar as LNG is a method for transporting natural gas, general demand for gas will play a role. According to EIA, annual gas usage in China will increase more than 2 Tcf by 2010, and worldwide demand seems strong as gas is increasingly seen as the fuel of choice for electricity generation. The EIA, the Gas Research Institute and other agencies believe gas drilling will need to be increased to meet future demand.

A great deal of research activity worldwide into LNG as a gasoline substitute could also create increased demand. Hundreds of LNG and CNG fueling stations are sprouting up around the world. Thus, future predictions are difficult, because advances in drilling, LNG processing economies, and new uses could shift the supply / demand balance to glut or shortage.

DOE funds studies. The University of Alaska-Fairbanks has been awarded a contract from the U.S. Department of Energy (DOE) to study the feasibility of transporting LNG through the Trans-Alaskan Pipeline System (TAPS). If a viable gas-to-liquids process could be established on the North Slope, "TAPS operations could be extended by 25 years or more ... and allow production of vast quantities of untapped natural gas beneath Alaska’s North Slope," says DOE.

In another project, DOE and the Bureau of Economic Geology at the University of Texas at Austin will join with gas producers in a $9-million study. The 4-yr effort will identify advanced technologies and methods for recovering bypassed natural gas in Gulf of Mexico fields. This is an extension of a land-based program that has enhanced gas production in the U.S. Midcontinent region. The program also added more than a billion dollars in new gas reserves in South Texas, where successful gas well completions jumped 24% from 1993 to 1996. According to DOE, studies have estimated that the U.S. might recover more than 500 Tcf — triple current proven gas reserves — by employing techniques identified in the program.

Big gas wells. Mobil has completed initial development of the Pase-A field — a satellite to the giant Arun gas complex in northern Sumatra — with three wells, each capable of supplying more than 100 MMcfgd to the Arun LNG plant. Production has been maximized by the successful application of underbalanced drilling. "The Pase-A well production rates are substantially higher than we initially expected," said R. I. Wilson, president and general manager of Mobil Oil Indonesia.

Mobil is also developing the North Sumatra Offshore-A field, located about 60 mi from the Arun plant, which is expected to be onstream next year. These fields, together with production from Arun and South Lhok Sukon fields, "Will help maintain LNG production well into the next century," said Wilson.

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